Laser apparatus, exposure head, exposure apparatus, and optical fiber connection method

ABSTRACT

An optical fiber of a bundled fiber light source is an optical fiber whose core diameter is uniform but whose emission end cladding diameter is smaller than an incidence end cladding diameter thereof, and a light emission region thereof is made smaller. An angle of luminous flux from this higher luminance bundled fiber light source, which passes through a lens system and is incident on a DMD, is smaller, i.e., an illumination NA is made smaller. Thus, an angle of flux which is incident on a surface that is to be exposed is smaller. That is, a minute image formation beam can be obtained without increasing the image formation NA, focal depth is lengthen.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser apparatus, an exposure head,and an exposure apparatus, and particularly relates to a suitablehigh-brightness laser apparatus which illuminates a spatiallight-modulation element, an exposure head which exposes aphotosensitive material with a laser beam modulated by a spatiallight-modulation element in accordance with image data, and an exposureapparatus equipped with this exposure head.

Furthermore, the present invention relates to an optical fiberconnection method and, in particular detail, to a method for connectingtwo optical fibers whose cladding diameters differ.

2. Description of the Prior Art

Heretofore, various exposure apparatuses which employ spatial lightmodulation elements such as digital micromirror devices (DMD) have beenproposed for carrying out image exposure with light beams modulated inaccordance with image data. An example of a DMD is a mirror device inwhich numerous micromirrors, which alter angles of reflection surfacesthereof in accordance with control signals, are arranged in atwo-dimensional pattern on a semiconductor support of silicon or thelike. An example of an exposure apparatus that utilizes such a DMD is,as shown in FIG. 15A, structured by a light source 1 which irradiateslaser light, a lens system 2 which collimates the laser light irradiatedfrom the light source 1, a DMD 3 which is disposed substantially at afocusing position of the lens system 2, and lens systems 4 and 6 whichfocus the laser light that has been reflected at the DMD 3 onto ascanning surface 5. In this exposure apparatus, the respectivemicromirrors of the DMD 3 are switched on and off by a control apparatus(not shown), in accordance with control signals generated in accordancewith image data or the like, and modulate the laser light. Thus, imageexposure is carried out by modulated laser light.

At the light source 1, a structural unit is plurally disposed. Thisstructural unit is equipped, as shown in FIG. 29, with a singlesemiconductor laser 7, a single multi-mode optical fiber 8, and a pairof collimator lenses 9. The pair of collimator lenses 9 focuses laserlight irradiated from the semiconductor laser 7 at an end face of themulti-mode optical fiber 8. The light source 1 is structured at abundle-form fiber light source in which a plurality of the multi-modeoptical fibers 8 are bundled.

Commonly, a laser with an output of around 30 mW (milliwatts) isemployed as the semiconductor laser 7, and an optical fiber with a corediameter of 50 μm, a cladding diameter of 125 μm and an NA (numericalaperture) of 0.2 is employed as the multi-mode optical fiber 8.Accordingly, if an output of around 1 W (watt) is to be obtained, it isnecessary to bundle a total of forty-eight (eight by six) of themulti-mode optical fibers 8 of the above-described structural units, anda diameter of the light emission point is about 1 mm.

However, in a conventional light source, the diameter of a lightemission point becomes larger in the event of bundling and,consequently, there is a problem in that sufficient depth of focuscannot be obtained when a high resolution exposure head is to bestructured. Sufficient focal depth cannot be obtained, in particular, inthe case of very high resolution exposure with a beam diameter of around1 μm. Moreover, beam blurring occurs at peripheral edge portions of anarea-form exposure beam.

Further, when a high power output exposure head is structured with aconventional exposure head, the number of optical fibers that arebundled increases. Thus, there are problems in that, not only do costsincrease, but diameter of a light emission point becomes larger, and theillumination NA with respect to the spatial light modulation elementalso becomes larger. As a result, the image formation NA of the imageformation beam becomes larger. Thus, focal depth becomes shallower.

SUMMARY OF THE INVENTION

The present invention has been devised in the hope of solving theproblems described above. A purpose of the present invention is toprovide a high-brightness laser apparatus that enables size reduction ofthe illumination NA with respect to the spatial light modulationelement. Another purpose of the present invention is to obtain a minuteimage formation spot without increasing the image formation NA of theimage formation beam, and to thereby provide an exposure head andexposure apparatus capable of providing deep focal depth. Yet anotherpurpose of the present invention is to provide an exposure head andexposure apparatus with high power outputs and low costs.

In order to achieve these purposes, a laser apparatus of the presentinvention includes a fiber light source which includes an optical fiberwith an incidence end and an emission end, the fiber light sourceemitting laser light that enters the incidence end of the optical fiberfrom the emission end of the optical fiber, wherein the optical fiberincludes an optical fiber having a uniform core diameter and a claddingdiameter of the emission end which is smaller than a cladding diameterof the incidence end.

Because the laser apparatus of the present invention is equipped withthe fiber light source which emits laser light that has entered throughthe incidence end of the optical fiber from the emission end thereof,and utilizes the optical fiber in which the core diameter is uniform butthe cladding diameter of the incidence end is smaller than the claddingdiameter of the emission end, a light emission portion diameter of thelight source can be made smaller and higher luminance can be provided.

The fiber light source may, for example, be a fiber light source with astructure in which a single semiconductor laser is joined at theincidence end of a single optical fiber. However, a multiplex laserlight source in which a plurality of laser lights are multiplexed andrespectively fed into an optical fiber is favorable. Higher output canbe obtained by employing a multiplex laser light source. Further, lightemission points at emission ends of optical fibers of a plurality offiber light sources can be arranged in an array pattern to form a fiberarray light source, or the respective light emission points can bearranged in the form of a bundle to form a fiber bundle light source.Even in such cases of bundling or arraying, the number of optical fibersthat are bundled/arrayed in order to obtain the same light output may besmaller, and costs are lower. Furthermore, when the number of opticalfibers is small, a light emission region when the optical fibers arebundled or arrayed can also be made small. In other words, luminance canbe made higher.

A multiplex laser light source may, for example, be: (1) a structurewhich includes a plurality of semiconductor lasers, a single opticalfiber, and a condensing optical system which condenses laser lightemitted from each of the plurality of semiconductor lasers and focusesthe condensed beams at the incidence end of the optical fiber; (2) astructure which includes a multi-cavity laser provided with a pluralityof light emission points, a single optical fiber, and a condensingoptical system which condenses laser light emitted from each of theplurality of light emission points and focuses the condensed beams atthe incidence face of the optical fiber; or (3) a structure whichincludes a plurality of multi-cavity lasers, a single optical fiber, anda condensing optical system which condenses laser light emitted fromeach of a plurality of light emission points of the plurality ofmulti-cavity lasers and focuses the condensed beams at the incidence endof the optical fiber.

From the viewpoint of the diameter of a light emission point beingsmall, it is preferable if the cladding diameter of the emission end ofthe optical fiber is smaller than 125 μm, more preferably 80 μm or less,and particularly preferably 60 μm or less. An optical fiber in which thecore diameter is uniform and the cladding diameter of the emission endis smaller than the cladding diameter of the incidence end may bestructured by, for example, joining a plurality of optical fibers withthe same core diameter and different cladding diameters. Furthermore,when a plurality of optical fibers are structured to be detachablyconnected with a connector or connectors, replacement in a case in whichthe light source module is partially damaged or the like is simple.

In order to achieve the aforementioned purposes, an exposure head of thepresent invention includes: the laser apparatus of the presentinvention; a spatial modulation element which modulates laser lightirradiated from the laser apparatus, the spatial modulation elementincluding numerous pixel portions, light modulation states of whichchange in accordance with respective control signals, the pixel portionsbeing arranged in a two-dimensional form on a support; and an opticalsystem for focusing laser light that has been modulated at the pixelportions on an exposure surface. Further, the exposure apparatus of thepresent invention includes: the exposure head of the present invention;and moving means which moves the exposure head relatively with respectto the exposure surface.

In the exposure head of the present invention and the exposure apparatusof the present invention, the spatial modulation element modulates thelaser light from the laser apparatus and controls exposure. Because thehigh-brightness laser apparatus is provided to serve as the laserapparatus, long focal depth can be obtained. Furthermore, in a case inwhich a multiplex laser light source at which a plurality of laserlights are multiplexed and fed into respective optical fibers isutilized as the fiber light source structuring the laser apparatus, highpower output can be obtained. Moreover, even in a case of bundling orarraying, the number of light fibers need only be small, and lower costscan be expected.

As the spatial modulation element, a micromirror device (a DMD: digitalmicromirror device) at which a large number of reflection surfaces,whose angles are adjustable in accordance with respective controlsignals, are arranged in a two-dimensional pattern on a micromirrorsupport (for example, a silicon support) can be utilized. Further, thespatial modulation element may be structured with a one-dimensionalgrating light valve (GLV) whose structure includes numerous movablegrilles and fixed grilles alternately disposed in parallel. The movablegrilles are provided with ribbon-like reflection surfaces and aremovable in accordance with control signals, and the fixed grilles areprovided with ribbon-like reflection surfaces. Further still, thespatial modulation element may be structured with a two-dimensionallight valve array in which GLVs are arranged in the form of an array.Further again, a liquid crystal shutter array whose structure includesnumerous liquid crystal cells, which are capable of blocking transmittedlight in accordance with respective control signals, arranged in atwo-dimensional pattern on a support may be utilized.

It is preferable if a microlens array is disposed at an emission side ofthe spatial modulation element. The microlens array is provided withmicrolenses which are provided in respective correspondence with pixelportions of the spatial modulation element and which condense laserlight from the respective pixels. In a case in which a microlens arrayis disposed thus, the laser lights that have been modulated at therespective pixel portions of the spatial modulation element arecondensed to correspond with respective pixels by the microlenses of themicrolens array. Consequently, even in a case in which an exposure areaat a surface to be exposed is enlarged, the size of each of beam spotscan be reduced, and exposure can be carried out with high precision.

It is also preferable if a collimator lens and a light intensitydistribution-correcting optical system are disposed between the laserapparatus and the spatial modulation element. The collimator lens makesluminous flux from the laser apparatus parallel flux. The lightintensity distribution-correcting optical system converts a flux widthat each of emission positions such that a ratio of a flux width at aperipheral edge portion to a flux width at a central portion, which isnear an optical axis, is smaller at an emission side of the lightintensity distribution-correcting optical system than at an incidenceside thereof, and corrects a light intensity distribution of the laserlight that has been converted to parallel flux by the collimator lens soas to be substantially uniform at irradiated faces of the spatialmodulation element.

As a result of this light intensity distribution-correcting opticalsystem, in which, for example, light with flux widths that are the sameat the incidence side, at the emission side, the flux width at thecentral portion is greater in comparison with the peripheral edgeportion and, conversely, the flux width at the peripheral edge portionis smaller in comparison with the central portion. Thus, because flux ofthe central portion can be brought to the peripheral edge portion, thespatial modulation element can be illuminated with light whose lightintensity distribution is substantially uniform, without reducing usageefficiency of the light as a whole. Consequently, a high quality imagecan be exposed at the exposed surface, without the occurrence ofexposure irregularities. Note that, a conventional rod integrator or afly-eye lens array may be utilized as the amount distribution correctionoptical system.

The spatial modulation element of the exposure head and exposureapparatus of the present invention can be controlled with controlsignals that are generated in accordance with exposure information foreach of a plurality of the pixel portions whose number is smaller thanthe total number of pixel portions arranged on the support. That is,rather than controlling all of the pixel portions arranged on thesupport, a subsection of the pixel portions can be controlled.Consequently, a transmission rate of the control signals can be madeshorter than in a case in which control signals are transmitted for allof the pixel portions, and a modulation rate of the laser light can bemade faster. As a result, high-speed exposure is possible.

Conventionally, in exposure devices which expose photosensitivematerials with ultraviolet-region laser light (ultraviolet exposuredevices), it has been common to employ gas lasers, such as argon lasersand the like, and solid lasers with THG (third harmonics). However,these exposure devices have had problems in that the devices are largeand difficult to maintain, and exposure speeds are slow. The exposureapparatus of the present invention can be made to serve as anultraviolet exposure device by utilizing a GaN-based (gallium nitride)semiconductor laser with a wavelength of 350 to 450 nm as the laserapparatus. This ultraviolet exposure device can be provided with smallersize and lower cost than the conventional ultraviolet exposure devices.Moreover, high speed, high accuracy exposure is possible.

The exposure device of the present invention may be suitably applied toan optical modelling device in which a light beam exposes aphoto-curable resin to form a three-dimensional model, a laminationmodelling device which sinters a powder with a light beam to formsintered layers and accumulates the sintered layers to form athree-dimensional model which is constituted by a sintered powder body,and the like.

An optical modelling device may, for example, be provided with amodelling tank which accommodates a photo-curable resin, a support tablewhich is for supporting a model and is movable up and down within themodelling tank, and an exposure head which includes: a laser apparatuswhich irradiates laser light; a spatial modulation element including alarge number of pixel portions whose light modulation states change inaccordance with respective control signals, and which are arranged in atwo-dimensional pattern on a support, and modulate the laser lightirradiated from the laser apparatus; and an optical system which focusesthe laser light that has been modulated by the respective pixel portionsonto a liquid surface of the photo-curable resin accommodated in themodelling tank. This optical modelling device is also provided withmoving means for moving the exposure head relative to the liquid surfaceof the photo-curable resin. If the laser apparatus of the presentinvention is utilized in this optical modelling device, high-speed,high-precision modelling is possible. A specific device structure isdisclosed in Japanese Patent Application No. 2001-274360.

A lamination modelling device may, for example, be provided with amodelling tank which accommodates a powder to be sintered by irradiationof light, a support table which is for supporting a model and is movableup and down within the modelling tank, and an exposure head whichincludes: a laser apparatus which irradiates laser light; a spatialmodulation element including a large number of pixel portions whoselight modulation states change in accordance with respective controlsignals, and which are arranged in a two-dimensional pattern on asupport, in accordance with respective control signals and modulate thelaser light irradiated from the laser apparatus; and an optical systemwhich focuses the laser light that has been modulated by the respectivepixel portions onto the surface of the powder accommodated in themodelling tank. This lamination modelling device is also provided withmoving means for moving the exposure head relative to the surface of thepowder. If the laser apparatus of the present invention is utilized inthis lamination modelling device, high-speed, high-precision modellingis possible. A specific device structure is disclosed in Japanese PatentApplication No. 2001-274351.

A further purpose of the present invention is to provide a methodcapable of reliably joining optical fibers which have a large differencein external diameters.

A first optical fiber connection method according to the presentinvention is a method for connecting two optical fibers with differentcladding diameters, which method includes the steps of: machiningcladding of one end portion of the optical fiber whose cladding diameteris larger to a diameter substantially the same as the cladding diameterof the optical fiber whose cladding diameter is smaller; and fusing theoptical fiber whose cladding diameter is smaller to the one end portionof the optical fiber that has been machined.

A second optical fiber connection method according to the presentinvention is similarly a method for connecting two optical fibers withdifferent cladding diameters, which method includes the steps of:machining cladding of one end portion of the optical fiber whosecladding diameter is larger to a diameter intermediate to the claddingdiameters of the two optical fibers; and fusing the optical fiber whosecladding diameter is smaller to the one end portion of the optical fiberthat has been machined.

A third optical fiber connection method according to the presentinvention is similarly a method for connecting two optical fibers withdifferent cladding diameters, which method includes the steps of: fusingone end portion of an optical fiber with a cladding diameterintermediate to the cladding diameters of the two optical fibers to theoptical fiber whose cladding diameter is larger; and fusing the otherend portion of the optical fiber with the intermediate cladding diameterto the optical fiber whose cladding diameter is smaller.

In the first optical fiber connection method according to the presentinvention, the cladding at the one end of the optical fiber whosecladding diameter is larger is machined to substantially the samediameter as the cladding diameter of the optical fiber whose claddingdiameter is small, and the optical fiber whose cladding diameter issmaller is fused to the one end portion of the optical fiber that hasbeen machined. Thus, fusion-splicing is applied to two optical fiberswhich have substantially the same cladding diameter. Accordingly, thetwo optical fibers can be easily and reliably joined without, as in acase in which two optical fibers whose diameters differ greatly arejoined by fusing, an optical fiber whose external diameter is smallerbeing excessively melted or, conversely, an optical fiber whose externaldiameter is larger not being melted.

In the second optical fiber connection method according to the presentinvention, the cladding at the one end of the optical fiber whosecladding diameter is larger is machined to an intermediate diameterbetween the cladding diameters of the two optical fibers, and theoptical fiber whose cladding diameter is smaller is fused to the one endportion of the optical fiber that has been machined. Thus,fusion-splicing is applied to two optical fibers whose claddingdiameters do not differ greatly. Accordingly, with this method too, theoptical fibers can be easily and reliably joined without, as in the casein which two optical fibers whose diameters differ greatly are joined byfusing, the optical fiber whose external diameter is smaller beingexcessively melted or, conversely, the optical fiber whose externaldiameter is larger not being melted.

In the third optical fiber connection method according to the presentinvention, the optical fiber whose cladding diameter is larger and theoptical fiber whose cladding diameter is smaller are joined by fusingvia an optical fiber therebetween which has an intermediate claddingdiameter between the cladding diameters of these two optical fibers.Thus, fusion-splicing is applied to the optical fiber having theintermediate cladding diameter and the optical fiber having the largercladding diameter and fusion-splicing is applied to the optical fiberhaving the intermediate cladding diameter and the optical fiber havingthe smaller cladding diameter, without cladding diameters of the pair ofoptical fibers in either case differing greatly. Accordingly, with thismethod too, the optical fibers can be easily and reliably joinedwithout, as in the case in which two optical fibers whose diametersdiffer greatly are joined by fusing, the optical fiber whose externaldiameter is smaller being excessively melted or, conversely, the opticalfiber whose external diameter is larger not being melted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the exterior of an exposureapparatus relating to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a structure of a scanner of theexposure apparatus relating to the first embodiment of the presentinvention.

FIG. 3A is a plan view showing exposed regions formed at aphotosensitive material.

FIG. 3B is a view showing an arrangement of exposure areas due torespective exposure heads.

FIG. 4 is a perspective view showing schematic structure of an exposurehead of the exposure apparatus relating to the first embodiment of theinvention.

FIG. 5A is a sectional view, cut in a sub-scanning direction along anoptical axis, showing structure of the exposure head shown in FIG. 4.

FIG. 5B is a side view showing a structure of the exposure head shown inFIG. 4.

FIG. 6 is a partial enlarged view showing a structure of a digitalmicromirror device (DMD).

FIGS. 7A and 7B are explanatory views for explaining operation of theDMD.

FIG. 8A is a plan view showing positions of exposure beams and scanninglines in a case in which the DMD is not disposed at an angle.

FIG. 8B is a plan view showing positions of exposure beams and scanninglines in a case in which the DMD is disposed at an angle.

FIG. 9A is a perspective view showing structure of a fiber array lightsource.

FIG. 9B is a partial enlarged view of the fiber array light source shownin FIG. 9A.

FIG. 9C is a plan view showing an arrangement of light emission pointsat a laser emission section.

FIG. 9D is a plan view showing another arrangement of light emissionpoints at a laser emission section.

FIG. 10 is a view showing structure of a multi-mode optical fiber.

FIG. 11 is a plan view showing structure of a multiplex laser lightsource.

FIG. 12 is a plan view showing structure of a laser module.

FIG. 13 is a side view showing structure of the laser module shown inFIG. 12.

FIG. 14 is a partial side view showing structure of the laser moduleshown in FIG. 12.

FIG. 15A is a sectional view, cut along the optical axis, showing depthof focus in a conventional exposure apparatus.

FIG. 15B is a sectional view, cut along the optical axis, showing depthof focus in the exposure apparatus relating to the first embodiment ofthe invention.

FIG. 16A is a view showing one row of an employed region of a DMD.

FIG. 16B is a view showing another row of the employed region of theDMD.

FIG. 17A is a side view showing a case in which the employed region ofthe DMD is appropriate.

FIG. 17B is a sectional view, cut in the sub-scanning direction alongthe optical axis, of FIG. 17A.

FIG. 18 is a plan view for explaining an exposure method for exposing aphotosensitive material with a single cycle of scanning by a scanner.

FIGS. 19A and 19B are plan views for explaining an exposure method forexposing a photosensitive material with a plurality of cycles ofscanning by a scanner.

FIG. 20 is a perspective view showing structure of a laser array.

FIG. 21A is a perspective view showing structure of a multi-cavitylaser.

FIG. 21B is a perspective view of a multi-cavity laser array in whichmulti-cavity lasers are arranged in the form of an array.

FIG. 22 is a plan view showing structure of another multiplex laserlight source.

FIG. 23 is a plan view showing structure of yet another multiplex laserlight source.

FIG. 24A is a plan view showing structure of still another multiplexlaser light source.

FIG. 24B is a sectional view, cut along the optical axis, of FIG. 24A.

FIGS. 25A, 25B and 25C are views for explaining concepts of correctionby a light intensity distribution-correcting optical system.

FIG. 26 is a graph showing a light intensity distribution in a case inwhich a light source has a gaussian distribution and correction of thelight intensity distribution is not carried out.

FIG. 27 is a graph showing a light intensity distribution aftercorrection by the light intensity distribution-correcting opticalsystem.

FIG. 28A is a sectional view, cut along the optical axis, showingstructure of another exposure head, in which a focusing optical systemis different.

FIG. 28B is a plan view showing an image which is projected onto asurface that is to be exposed in a case in which a microlens array orthe like is not employed.

FIG. 28C is a plan view showing an image which is projected onto thesurface that is to be exposed in a case in which the microlens array orthe like is employed.

FIG. 29 is a sectional view, cut along the optical axis, showingstructure of a conventional fiber light source.

FIG. 30 is a perspective view showing schematic structure of an exposurehead of an exposure apparatus relating to a second embodiment of theinvention.

FIG. 31A is a sectional view, cut along the optical axis, showingstructure of the exposure head shown in FIG. 30.

FIG. 31B is a side view showing structure of the exposure head shown inFIG. 31A.

FIG. 32 is a partial enlarged view showing structure of a grating lightvalve (GLV).

FIGS. 33A and 33B are explanatory views for explaining operation of theGLV.

FIG. 34 is a perspective view showing an example in which the presentinvention is applied in an optical modelling device.

FIG. 35A is a perspective view showing structure of a fiber bundle lightsource.

FIG. 35B is a perspective view showing structure of a different fiberarray light source.

FIG. 36 is a plan view showing an end face of a laser emission portionof a bundle-form fiber light source.

FIGS. 37A and 37B are views for explaining one example of an opticalfiber connection method.

FIG. 38 is a view for explaining another example of an optical fiberconnection method.

FIG. 39 is a view for explaining yet another example of an optical fiberconnection method.

FIG. 40 is a view showing structure of a multi-mode optical fiber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, embodiments of the present invention will be described in detailwith reference to the drawings.

First Embodiment

Structure of Exposure Apparatus

As shown in FIG. 1, an exposure apparatus relating to an embodiment ofthe present invention is provided with a flat board-form stage 152,which sucks and retains a sheet-form photosensitive material 150 at asurface thereof. Two guides 158, which extend in a stage movementdirection, are provided at an upper face of a thick board-form equipmentpedestal 156, which is supported by four leg portions 154. The stage 152is disposed such that a longitudinal direction thereof is oriented inthe stage movement direction, and is supported by the guides 158 so asto be movable reciprocally. In the exposure apparatus, an unillustrateddriving apparatus is provided for driving the stage 152 along the guides158.

At a central portion of the equipment pedestal 156, an inverted ‘U’-likegate 160 is provided so as to straddle a movement path of the stage 152.Respective end portions of the inverted ‘U’-like gate 160 are fixed attwo side faces of the equipment pedestal 156. Sandwiching the gate 160,a scanner 162 is provided at one side, and a plurality (for example,two) of detection sensors 164 are provided at the other side. Thedetection sensors 164 detect a leading end and a trailing end of thephotosensitive material 150. The scanner 162 and the detection sensors164 are respectively mounted at the gate 160, and are fixedly disposedupward of the movement path of the stage 152. The scanner 162 anddetection sensors 164 are connected to an unillustrated controller whichcontrols the scanner 162 and detection sensors 164.

As shown in FIGS. 2 and 3B, the scanner 162 is equipped with a plurality(for example, fourteen) of exposure heads 166, which are arrangedsubstantially in a matrix pattern with m rows and n columns (forexample, three rows and five columns). In this example, in considerationof width of the photosensitive material 150, four of the exposure heads166 are provided in the third row. Note that when an individual exposurehead, which is arranged in the m-th row and the n-th column is to bereferred to, that exposure head is denoted as exposure head 166 _(mn).

Exposure areas 168 covered by the exposure heads 166 have rectangularshapes with short sides thereof in a sub-scanning direction.Consequently, in accordance with movement of the stage 152, band-formexposed regions 170 are formed on the photosensitive material 150 at therespective exposure heads 166. Note that when an exposure area formed byan individual exposure head, which is arranged in the m-th row and then-th column, is to be referred to, that exposure area is denoted asexposure area 168 _(mn).

As shown in FIGS. 3A and 3B, in each row, the respective exposure heads,which are arranged in a line, are disposed to be offset by apredetermined interval in a row arrangement direction (which interval isan integer multiple (two in the present embodiment) of the longdimension of the exposure areas), such that the band-form exposedregions 170 will be lined up without gaps therebetween in a directionintersecting the sub-scanning direction. Thus, a portion that cannot beexposed between exposure area 168 ₁₁ and exposure area 168 ₁₂ of thefirst row can be exposed by exposure area 168 ₂₁ of the second row andexposure area 168 ₃₁ of the third row.

As shown in FIGS. 4, 5A and 5B, at each of the exposure areas 166 ₁₁ to166 _(mn), a digital micromirror device (DMD) 50 is provided to serve asa spatial modulation element for modulating an incident light beam ateach of pixels in accordance with image data. The DMD 50 is connectedwith an unillustrated controller, which is provided with a dataprocessing section and a mirror driving control section. At the dataprocessing section of this controller, on the basis of inputted imagedata, driving signals are generated for driving control of eachmicromirror in a region of the DMD 50 at the corresponding exposure head166 which region is to be controlled. The regions that are to becontrolled are described later. The mirror driving control sectioncontrols the angle of a reflection surface of each micromirror of theDMD 50 at the corresponding exposure head 166, on the basis of thecontrol signals generated at the image data processing section. Controlof the angles of the reflection faces is described later.

At a light incidence side of the DMD 50, a fiber array light source 66,a lens system 67 and a mirror 69 are disposed in this order. The fiberarray light source 66 is equipped with a laser emission section in whichemission end portions (light emission points) of optical fibers arearranged in a row along a direction corresponding to the direction ofthe long sides of the exposure area 168. The lens system 67 correctslaser light that is emitted from the fiber array light source 66, andfocuses the light on the DMD. The mirror 69 reflects the laser lightthat has been transmitted through the lens system 67 toward the DMD 50.

The lens system 67 is structured with a single pair of combinationlenses 71, which make the laser light that has been emitted from thefiber array light source 66 parallel, a single pair of combinationlenses 73, which correct the laser light that has been made parallelsuch that a light intensity distribution is uniform, and a condensinglens 75 that focuses the laser light whose light intensity distributionhas been corrected on the DMD. The combination lenses 73 have thefunctions of, in the direction of arrangement of the laser emissionends, broadening portions of luminous flux that are close to an opticalaxis of the lenses and narrowing portions of the luminous flux that aredistant from the optical axis, and in a direction intersecting thisdirection of arrangement, transmitting the light unaltered. Thus, thelaser light is corrected such that the light intensity distribution isuniform. Here, an example of means for correcting distribution of thelight intensity has been shown. However, conventionally known means formaking the distribution of the light intensity uniform, such as rodintegrator, fly-eye lens array or the like, may be used.

Lens systems 54 and 58 are disposed at a light reflection side of theDMD 50. The lens systems 54 and 58 focus the laser light that has beenreflected at the DMD 50 on a scanning surface (a surface that is to beexposed) 56 of the photosensitive material 150. The lens systems 54 and58 are disposed such that the DMD 50 and the surface to be exposed 56have a conjugative relationship.

As shown in FIG. 6, at the DMD 50, very small mirrors (micromirrors) 62,which are supported by support columns, are disposed on an SRAM cell(memory cell) 60. The DMD 50 is a mirror device which is structured witha large number (for example, 600 by 800) of these extremely smallmirrors, which structure picture elements (pixels), arranged in acheckerboard pattern. At each pixel, the micromirror 62 is provided soas to be supported at an uppermost portion of the support column. Amaterial with high reflectivity, such as aluminum or the like, isapplied by vapor deposition on the surface of the micromirror 62. Here,the reflectivity of the micromirror 62 is at least 90%. An SRAM cell 60with CMOS silicon gates, which is fabricated by a usual semiconductormemory production line, is disposed directly under the micromirror 62,with the support column, which includes a hinge and a yoke, interposedtherebetween. The whole of this structure is monolithic (integrated).

When digital signals are written to the SRAM cell 60 of the DMD 50, themicromirrors 62 supported at the support columns are inclined, about adiagonal of the micromirror 62, within a range of ±α° (for example,±10°), relative to the side of the support at which the DMD 50 isdisposed. FIG. 7A shows a state in which the micromirror 62 is inclinedat +α°, which is an ‘ON’ state, and FIG. 7B shows a state in which themicromirror 62 is inclined at −α°, which is an ‘OFF’ state. Accordingly,as a result of control of the inclinations of the micromirrors 62 at thepixels of the DMD 50 in accordance with image signals, as shown in FIG.6, light that is incident at the DMD 50 is reflected in directions ofinclination of the respective micromirrors 62.

FIG. 6 shows a portion of the DMD 50 enlarged, and shows an example of astate in which the micromirrors 62 are controlled to +α° and −α°. TheON-OFF control of the respective micromirrors 62 is carried out by theunillustrated controller connected to the DMD 50. A light-absorbing body(which is not shown) is disposed in the direction in which light beamsare reflected by the micromirrors 62 that are in the OFF state.

It is preferable if the DMD 50 is disposed to be slightly inclined, suchthat a short side thereof forms a predetermined angle θ (for example, 1°to 5°) with the sub-scanning direction. FIG. 8A shows scanning tracks ofreflected light images (exposure beams) 53 formed by the micromirrors ina case in which the DMD 50 is not inclined. FIG. 8B shows scanningtracks of the exposure beams) 53 in the case in which the DMD 50 isinclined.

At the DMD 50, a large number (for example, 800) of micromirrors arearranged in a long side direction to form a micromirror row, and a largenumber (for example, 600) of these micromirror rows are arranged in ashort side direction. As shown in FIG. 8B, when the DMD 50 is inclined,a pitch P2 of scanning paths (scanning lines) of the exposure beams 53from the micromirrors is tighter than a pitch PI of scanning lines inthe case in which the DMD 50 is not inclined. Thus, resolution can begreatly improved. However, because the angle of inclination of the DMD50 is very small, a scanning width W2 in the case in which the DMD 50 isinclined is substantially the same as a scanning width W1 in the case inwhich the DMD 50 is not inclined.

The same scanning line will be superposingly exposed by differentmicromirror rows (multiple exposure). As a consequence of this multipleexposure, exposure positions can be controlled in very fine amounts, andhigh accuracy exposure can be implemented. Further, by control in veryfine amounts of exposure positions at boundary lines between theplurality of exposure heads arranged in a main scanning direction, joinswithout steps can be formed.

Instead of inclining the DMD 50, the micromirrors may be disposed in astaggered pattern in which the micromirror rows are shifted bypredetermined intervals in the direction intersecting the sub-scanningdirection, and the same effects can be obtained.

As shown in FIG. 9A, the fiber array light source 66 is equipped with aplurality (for example, six) of laser modules 64. At each of the lasermodules 64, one end of a multi-mode optical fiber 30 is connected. Atthe other end of the multi-mode optical fiber 30, an optical fiber 31,whose core diameter is the same as that of the multi-mode optical fiber30 and whose cladding diameter is smaller than that of the multi-modeoptical fiber 30, is connected. As shown in FIG. 9C, emission endportions of the multi-mode optical fibers 31 (light emission points) arearranged in a single row along the main scanning direction, whichintersects the sub-scanning direction, to structure a laser emissionportion 68. Note that the light emission points may be arranged in tworows along the main scanning direction, as shown in FIG. 9D.

As is shown in FIG. 9B, the emission end portions of the optical fibers31 are inserted between a pair of support plates 65, which have flatfaces.

In this example, because the emission ends of the optical fibers 31 withsmall cladding diameters are arranged in a single row without gapstherebetween, some of the multi-mode optical fibers 30, which are eachbetween two of the multi-mode optical fibers 30 that are adjacent at thesection with large cladding diameters, are piled up on the adjacent twoof the multi-mode optical fibers 30. The emission end of the opticalfiber 31 that is joined to the multi-mode optical fiber 30 that is piledup is arranged so as to be sandwiched between the two emission ends ofthe multi-mode optical fibers 31 that are joined to the two multi-modeoptical fibers 31 that are adjacent at the section with large claddingdiameters.

These optical fibers, as shown in FIG. 10, for example, can be obtainedby coaxially joining 1 to 30 cm lengths of the optical fibers 31 withsmall diameters to distal end portions, at the laser light emissionside, of the multi-mode optical fibers 30 with large cladding diameters.The two types of optical fiber are joined by fusing incidence end facesof the optical fibers 31 to emission end faces of the multi-mode opticalfibers 30 such that central axes of the pairs of fibers coincide. Asdescribed above, a diameter of a core 31 a of the optical fiber 31 hasthe same magnitude as a diameter of a core 30 a of the multi-modeoptical fiber 30.

A short-strip optical fiber, at which the optical fiber whose claddingdiameter is smaller is fused to an optical fiber whose length is shortand whose cladding diameter is larger, may be joined at the emission endof the multi-mode optical fiber 30 via a ferrule, an optical connectoror the like. Because the joining is carried out using the connector orthe like so as to be detachable, replacement of a peripheral endportion, in a case in which the optical fiber whose cladding diameter issmall has been damaged or the like, is simple and costs required formaintenance of the exposure head can be reduced.. Hereafter, the opticalfiber 31 may on occasions be referred to as an exposure end portion ofthe multi-mode optical fiber 30.

As the multi-mode optical fiber 30 and the multi-mode optical fiber 31,any of step index-type optical fibers, graded index-type optical fibersand multiplex-type optical fibers can be used. For example, a stepindex-type optical fiber produced by Mitsubishi Cable Industries, Ltd.can be used. In the present embodiment, the multi-mode optical fiber 30and the optical fiber 31 are step index-type optical fibers. Themulti-mode optical fiber 30 has cladding diameter=125 μm, corediameter=25 μm, NA=0.2, and transmittance of an end face coating=99.5%or more. The optical fiber 31 has cladding diameter=60 μm, corediameter=25 μm, and NA=0.2.

Commonly, with laser light in the infrared region, propagation lossesincrease as the cladding diameter of an optical fiber becomes smaller.Therefore, suitable cladding diameters are determined in accordance witha wavelength range of laser light. However, the shorter the wavelength,the smaller the propagation losses. Thus, with laser light with awavelength of 405 nm, emitted from a GaN-based semiconductor laser,propagation losses are barely increased at all in a case in which acladding thickness ((cladding diameter−core diameter)/2) is around halfthat for a case of propagating infrared light in an 800 nm wavelengthregion or around a quarter that for a case of propagating infrared lightin a 1.5 μm wavelength region, the latter of which is used forcommunications. Accordingly, the cladding diameter can be reduced to 60μm. Therefore, by utilizing, in place of the infrared laser, a GaN-basedsemiconductor laser, which is a shorter wavelength light source, enablesto make the cladding diameter can be reduced to a value substantiallythe same as the core diameter. Thus, by arranging the optical fibershaving a small cladding in an array, or in other words, by disposing theoptical fibers having a diameter substantially the same as the corediameter in an array it becomes highly possible to obtain a veryhigh-brightness light source. However, the cladding diameter of theoptical fiber 31 is not limited to 60 μm. An optical fiber which isemployed in a conventional fiber light source has a cladding diameter of125 μm. However, because focal depth becomes deeper as the claddingdiameter become smaller, it is preferable if the cladding diameter is 80μm or less, more preferably 60 μm or less, and even more preferably 40μm or less. On the other hand, given that the core diameter needs to beat least 3 to 4 μm, it is preferable that the cladding diameter of theoptical fiber 31 is at least 10 μm.

The laser module 64 is structured by a multiplexed laser light source(fiber light source) shown in FIG. 11. This multiplex laser light sourceis structured with a plurality (for example, seven) of chip-form lateralmulti-mode or single-mode GaN-based semiconductor lasers LD1, LD2, LD3,LD4, LD5, LD6 and LD7, collimator lenses 11, 12, 13, 14, 15, 16 and 17,a single condensing lens 20, and one of the multi-mode optical fibers30. The GaN-based semiconductor lasers LD1 to LD7 are fixedly arrangedon a heat block 10. The collimator lenses 11 to 17 are provided incorrespondence with the GaN-based semiconductor lasers LD1 to LD7,respectively. The number of semiconductor lasers is not limited toseven. As many as twenty semiconductor lasers may be fed into amulti-mode optical fiber with cladding diameter=60 μm, core diameter=50μm and NA=0.2. Thus, a light intensity required from the exposure headcan be realized, and/or the number of optical fibers can be furtherreduced.

The GaN-based semiconductor lasers LD1 to LD7 all have a commonoscillation wavelength (for example, 405 nm), and a common maximumoutput (for example, 100 mW with multi-mode lasers, 30 mW withsingle-mode lasers). For the GaN-based semiconductor lasers LD1 to LD7,lasers can be utilized which are provided with an oscillation wavelengthdifferent from the above-mentioned 405 nm, in a wavelength range of 350nm to 450 nm.

As shown in FIGS. 12 and 13, the above-described multiplex laser lightsource, together with other optical elements, is accommodated in abox-like package 40 a top of which is opened. The package 40 is providedwith a package lid 41 prepared so as to close the opening of the package40. After an air removal treatment, sealed gas is introduced inside thepackage and the opening of the package 40 is closed by the package lid41. Thus, the above-described multiplex laser light source ishermetically sealed in a closed space (sealed space) formed by thepackage 40 and the package lid 41.

A base plate 42 is fixed at a lower face of the package 40. The heatblock 10, a condensing lens holder 45 and a fiber holder 46 are attachedat an upper face of the base plate 42. The condensing lens holder 45holds the condensing lens 20. The fiber holder 46 holds an incidence endportion of the multi-mode optical fiber 30. An opening is formed in awall face of the package 40, and the emission end portion of themulti-mode optical fiber 30 is passed through this opening and led outto the outside of the package.

A collimator lens holder 44 is attached at a side face of the heat block10, and holds the collimator lenses 11 to 17. Openings are formed in alateral wall face of the package 40. Wiring 47, which supplies drivingcurrent to the GaN-based semiconductor lasers LD1 to LD7, is passedthrough these openings and led out to outside the package.

Note that in FIG. 13, in order to avoid complexity of the drawing, ofthe plurality of GaN-based semiconductor lasers, only the GaN-basedsemiconductor laser LD7 is marked with a reference numeral, and of theplurality of collimator lenses, only the collimator lens 17 is markedwith a reference numeral.

FIG. 14 shows front face configurations of attachment portions of thecollimator lenses 11 to 17. Each of the collimator lenses 11 to 17 has along, narrow, cut-down shape with parallel flat faces defining a regionthat includes an optical axis of a circular-form lens which is providedwith an aspherical surface. The collimator lenses with this long, narrowshape can be formed, for example, by molding-formation of resin oroptical glass. The collimator lenses 11 to 17 are closely disposed in adirection of arrangement of light emission points of the GaN-basedsemiconductor lasers LD1 to LD7 (the left-right direction in FIG. 14)such that the longitudinal directions of the collimator lenses 11 to 17cross the direction of arrangement of the light emission points at rightangles.

As the GaN-based semiconductor lasers LD1 to LD7, lasers may be employedwhich are provided with an active layer with a light emission width of 2μm, and which respectively emit laser beams B1 to B7 in forms whichwiden at angles of, for example, 10° and 30° with respect, respectively,to a direction parallel to the active layers and a directionperpendicular to the active layers. These GaN-based semiconductor lasersLD1 to LD7 are disposed such that the light emission points are lined upin a single row in the direction parallel to the active layers.

Accordingly, the laser beams B1 to B7 emitted from the respective lightemission points are incident, respectively, on the collimator lenses 11to 17 having the long, narrow forms described above, in states in whichthe direction for which the spreading angle of the beam, which isgreater, is greater coincides with the longitudinal direction of thelens and the direction in which the spreading angle is smaller coincideswith a width direction (a direction intersecting the longitudinaldirection at right angles). Specifically, the width of each of thecollimator lenses 11 to 17 is 1.1 mm and the length thereof is 4.6 mm,and the laser beams B1 to B7 incident thereat have beam diameters in thehorizontal direction and the vertical direction of 0.9 mm and 2.6 mm,respectively. Further, each of the collimator lenses 11 to 17 has afocal length f1=3 mm, NA=0.6 and lens arrangement pitch=1.25 mm.

The condensing lens 20 is cut away in a long, narrow shape with parallelflat faces defining a region that includes an optical axis of acircular-form lens which is provided with an aspherical surface, and isformed in a shape which is long in the direction of arrangement of thecollimator lenses 11 to 17 (i.e., the horizontal direction) and short ina direction perpendicular thereto. The condensing lens 20 has a focallength f2=23 mm and NA=0.2. Since the wavelength is about 400 nm, aminute spot diameter that sufficiently enables joining with highefficiency for a core diameter of 50 μm can be obtained. The condensinglens 20 is also formed by, for example, molding-formation of resin oroptical glass.

Operation of the Exposure Apparatus

Next, operation of the exposure apparatus described above will beexplained.

In the exposure heads 166 of the scanner 162, the respective laser beamsB1, B2, B3, B4, B5, B6 and B7, which are emitted in divergent forms fromthe respective GaN-based semiconductor lasers LD1 to LD7 that structurethe multiplex laser light source of the fiber array light source 66, areconverted to parallel light by the corresponding collimator lenses 11 to17. The laser beams B 1 to B7 that have been collimated are focused bythe condensing lens 20, and converge at the incidence end face of thecore 30 a of the multi-mode optical fiber 30.

In the present example, a condensing optical system is structured by thecollimator lenses 11 to 17 and the condensing lens 20, and amultiplexing optical system is structured by the condensing opticalsystem and the multi-mode optical fiber 30. Thus, the laser beams B1 toB7 focused by the condensing lens 20 as described above enter the core30a of the multi-mode optical fiber 30, are propagated in the opticalfiber, multiplexed to a single laser beam B, coupled at the emission endportion of the multi-mode optical fiber 30, and emitted from the opticalfiber 31.

In each laser module, a coupling efficiency of the laser beams B1 to B7into the multi-mode optical fiber 30 is 0.85. Therefore, in a case inwhich the respective outputs of the GaN-based semiconductor lasers LD1to LD7 are 30 mW, the multiplexed laser beam B can be obtained with anoutput of 180 mW (=30 mW×0.85×7) from each of the optical fibers 31arranged in the array pattern. Accordingly, output of the laser emissionportion 68 in which six of the optical fibers 31 are arranged in thearray pattern is approximately 1 W (=180 mW×6).

At the laser emission portion 68 of the fiber array light source 66,high-brightness light emission points as described above are arranged ina single row along the main scanning direction. Because a conventionalfiber light source, in which laser light from a single semiconductorlaser is focused at a single optical fiber, has low output, a desiredoutput cannot be obtained without arranging these conventional lightsources in a large number of rows. However, because the multiplex laserlight source employed in the present embodiment has high power output, adesired output can be obtained with only a small number of rows, forexample, one row.

For example, in a conventional fiber light source, in whichsemiconductor lasers are joined with optical fibers in a one-to-onerelationship, lasers with outputs of around 30 mW (milliwatts) arecommonly employed as the semiconductor lasers, and multi-mode opticalfibers with core diameter 50 μm, cladding diameter 125 μm, and NA(numerical aperture) 0.2 are employed as the optical fibers. Therefore,if an output of around 1 W (watt) is to be obtained, forty-eight (8×6)multi-mode optical fibers must be bundled. Thus, from a light emissionregion with an area of 0.62 mm² (0.675 mm by 0.925 mm), luminance ofthis laser emission portion 68 is 1.6×106 W/m², and luminance from eachoptical fiber is 3.2×10⁶ W/m².

In contrast, in the present embodiment, an output of approximately 1 Wcan be provided by six multi-mode optical fibers, as described above.Thus, from a light emission region of the laser emission portion 68 withan area of 0.0081 mm² (0.325 mm×0.025 mm), luminance of the laseremission portion 68 is 123×10⁶ W/m². Thus, a luminance about eightytimes higher than in the conventional case can be expected. Furthermore,the luminance from each optical fiber is 90×10⁶ W/m². Thus, a luminancearound twenty-eight times higher than in the conventional case can beexpected. As described above, a light source having a high-brightnesscan be obtained. Particularly, since a shorter wavelength light sourcesuch as a GaN-based light source can be utilized, a minute spot can beobtained even at the same condensing NA (i.e., fiber incident NA), and afiber light source and a fiber array or bundle having a higher luminancecan be obtained. As a result, since the laser light has a shorterwavelength, the image formation beam can be formed in a minute spot, andthus, high energy density and strong photon energy can be obtained. Dueto these two effects, the light source may be utilized not only forchemical alteration, such as photochemical polymerization, but for broadapplications, such as sintering, annealing and metal machining which usephysical alteration.

Further, since the light source is a high-brightness light source, aminute image formation beam can be secured even by a small imageformation NA, and even in digital exposure using a spatial lightmodulation element, an illumination NA for the spatial light modulationelement can be made smaller. As a result, the size of the spatial lightmodulation element can be reduced, and transmission speed orlight-switching speed can be easily improved, and high speed and highprecision exposure can be carried out.

Furthermore, by utilizing a semiconductor laser, photon cost can begreatly reduced. Further, since turning the light source ON and OFF canbe easily carried out and life of the light source can be lengthen, thelight source can be made maintenance free, and reduction in cost of thelight source sufficient to allow broad application thereof can berealized for the first time.

Moreover, an optical fiber is easy to handle and-easy to replace.Therefore, the light source can be utilized for various uses.

Now, a difference in focal depth between the conventional exposure headand the exposure head of the present embodiment will be described withreference to FIGS. 15A and 15B. A diameter in the sub-scanning directionof the light-emitting region of the bundle-form fiber light source ofthe conventional exposure head is 0.675 mm, whereas the diameter in thesub-scanning direction of the light-emitting region of the fiber arraylight source of the exposure head of the present embodiment is 0.025 mm.As shown in FIG. 15A, with the conventional exposure head, because thelight-emitting region of the light source 1 (the bundle-form fiber lightsource) is large, the angle of luminous flux incident on the DMD 3 islarge. Hence, the angle of luminous flux incident on the scanningsurface 5 is large. Consequently, the beam diameter is susceptible tobroadening with respect to a condensing direction (displacement in adirection of focusing).

In contrast, as shown in FIG. 15B, with the exposure head of the presentembodiment, the diameter in the sub-scanning direction of thelight-emitting region of the fiber array light source 66 is smaller.Hence, the angle of luminous flux that has passed through the lenssystem 67 and is incident on the DMD 50 is smaller. Consequently, theangle of luminous flux incident on the scanning surface 56 is smaller.That is, the focal depth is longer. In this example, the diameter in thesub-scanning direction of the light-emitting region is about a thirtieththat in the conventional case, and a focal depth substantiallycorresponding to the diffraction limit can be obtained. Accordingly, thepresent embodiment is excellent for exposure with very fine spots. Theeffect on the focal depth is particularly remarkable when the lightintensity required from the exposure head is large, which is useful. Inthis example, the size of one pixel as projected on the exposure surfaceis 10 μm by 10 μm. Note that, although the DMDs are reflection-typespatial modulation elements, FIGS. 15A and 15B are expanded views, forthe purpose of explaining optical relationships.

Image data corresponding to an exposure pattern is inputted at theunillustrated controller connected to the DMD 50, and is temporarilystored in a frame memory in the controller. This image data is datawhich represents a density of each pixel structuring an image with abinary value (whether or not a dot is to be recorded).

The stage 152, at which the surface of the photosensitive material 150is sucked and attached, is moved along the guides 158 at a constantspeed by the driving apparatus, from an upstream side of the gate 160 toa downstream side thereof. When the stage 152 is passing under theexposure areas 168, and the leading end of the photosensitive material150 has been detected by the detection sensors 164 attached at the gate160, the image data stored in the frame memory is read out as aplurality of line portion units in sequence, and control signals foreach of the exposure heads 166 are generated on the basis of the imagedata read from the data processing section. Hence, the micromirrors ofthe DMDs 50 at the respective exposure heads 166 are respectivelyswitched on and off by the mirror driving control section on the basisof the control signals that have been generated.

When laser light is irradiated from the fiber array light source 66 tothe DMD 50, if a micromirror of the DMD 50 is in the ON state, thereflected laser light is focused on the surface to be exposed 56 of thephotosensitive material 150 by the lens systems 54 and 58. Thus, thelaser light irradiated from the fiber array light source 66 is turned onor off at each pixel, and the photosensitive material 150 is exposed ina unit with a number of pixels substantially the same as the number ofpixels employed at the DMD 50 (the exposure area 168). Furthermore, asthe photosensitive material 150 is moved together with the stage 152 atthe constant speed, the photosensitive material 150 is scanned in adirection opposite to the stage movement direction by the scanner 162,and the strip-form exposed regions 170 are formed at the respectiveexposure heads 166.

As shown in FIGS. 16A and 16B, at the DMD 50 in the present embodiment,600 micromirror rows, in each of which 800 of the micromirrors arearranged in the main scanning direction, are arranged in thesub-scanning direction. However, control by the controller so as todrive only a portion of the micromirror rows (for example, 800micromirrors by 100 rows) is possible.

Micromirror rows that are disposed at a central portion of the DMD 50may be employed, as shown in FIG. 16A, and micromirror rows that aredisposed at an end portion of the DMD 50 may be employed, as shown inFIG. 16B. Further, in a case in which defects have occurred at some ofthe micromirrors, the micromirror rows that are to be employed may besuitably changed in accordance with the situation, by employingmicromirror rows in which defects have not occurred, or the like.

There is a limit to a data processing speed of the DMD 50, and amodulation rate for one line is determined in proportion to the numberof pixels employed. Thus, the modulation rate for one line can beaccelerated by employing only a portion of the micromirror rows.Further, in the case of an exposure method in which the exposure head iscontinuously moved relative to the exposure surface, there is no need toemploy all pixels in the sub-scanning direction.

For example, in a case in which only 300 of the 600 rows of micromirrorsare employed, modulation is possible at twice the rate for one line asin a case in which all 600 lines are employed. Further, in a case inwhich only 200 of the 600 rows of micromirrors are employed, modulationis possible three times as quickly for one line as in the case ofemploying all 600 lines. Specifically, a region which is 500 mm in thesub-scanning direction can be exposed in 17 seconds. Furthermore, in acase in which only 100 lines are employed, modulation for one line canbe done six times as quickly. That is, a region which is 500 mm in thesub-scanning direction can be exposed in 9 seconds.

The number of micromirror rows that are employed, that is, the number ofmicromirrors arranged in the sub-scanning direction, is preferably atleast 10 and at most 200, and is more preferably at least 10 and at most100. An area corresponding to one micromirror, which corresponds to onepixel, is 15 μm×15 μm. Therefore, when an employed region of the DMD 50is reduced, it is preferable that this region is at least 12 mm by 150μm and at most 12 mm by 3 mm, and more preferably at least 12 mm by 150μm and at most 12 mm by 1.5 mm.

If the number of micromirrors that are employed is within the rangesdescribed above, the laser light that is irradiated from the fiber arraylight source 66 can be made substantially parallel by the lens system 67and irradiated at the DMD 50, as shown in FIGS. 17A and 17B. It ispreferable if an irradiated region of the DMD 50 which is irradiatedwith the laser light substantially coincides with the region of the DMD50 that is employed. If the irradiated region is larger than theemployed region, then usage efficiency of the laser light will fall.

There is a requirement that the diameter in the sub-scanning directionof the light beam that is focused on the DMD 50 is made smaller by thelens system 67, in accordance with the number of micromirrors arrangedin the sub-scanning direction. Thus, if the number of micromirror rowsthat are employed is less than 10, the angle of the luminous fluxincident at the DMD 50 will be large, and the focal depth of the lightbeam at the surface to be exposed 56 will be shallow, which is notpreferable. In addition, the number of micromirror rows that areemployed is preferable to be less than 200 or less from the viewpoint ofmodulation rate. Note that, although the DMD is a reflection-typespatial modulation element, FIGS. 17A and 17B are expanded views, forthe purpose of explaining optical relationships.

When sub-scanning of the photosensitive material 150 by the scanner 162has been completed and the trailing end of the photosensitive material150 has been detected by the detection sensors 164, the stage 152 isdriven back along the guides 158 by the unillustrated driving apparatus,to a start point at an upstream-most side of the gate 160, and is againmoved along the guides 158, at a constant speed, from the upstream sideto the downstream side of the gate 160.

As has been described above, the exposure apparatus of the presentembodiment is provided with an exposure head in which a fiber arraylight source, at which emission end portions (light emission points) ofoptical fibers of a multiplex laser light source are arranged in anarray pattern, irradiates a spatial modulation element. At this fiberarray light source, because cladding diameters of emission ends of theoptical fibers are set to be smaller than cladding diameters ofincidence ends thereof, light emission portion diameters are smaller anda fiber array light source with a higher luminance can be provided.Consequently, an exposure head and exposure apparatus featuring a deepfocal depth can be realized. For example, in a case of very highresolution exposure with a beam diameter of 1 μm or less and aresolution of 0.1 μm or less, a long focal depth can be obtained, andbeam blurring at peripheral edge portions of an area-type exposure beamcan be suppressed. Thus, high-speed, high-precision exposure ispossible. Accordingly, the exposure apparatus of the present embodimentcan be employed even for thin film transistor (TFT) exposure processesand the like, which require high resolution.

Further, because a multiplex laser light source in which a plurality oflaser lights are multiplexed and fed into an optical fiber is used,output at the emission end of the optical fiber is greater, and exposurewith a high power output is possible. Further still, because the outputof each fiber light source is greater, the number of fiber light sourcesrequired for providing a desired output is smaller, and reducing incosts of the exposure apparatus can be provided.

Further yet, the exposure apparatus of the present embodiment isprovided with a DMD in which 600 micromirror rows are arranged in thesub-scanning direction with 800 micromirrors being arranged in the mainscanning direction in each of the micromirror rows. However, by acontroller controlling so as to drive only some of the micromirror rows,a modulation rate for one line can be made faster than in a case inwhich all of the micromirror rows are driven. Thus, exposure at highspeed is possible.

Second Embodiment

An exposure apparatus relating to a second embodiment utilizes gratinglight valves (GLV) as spatial light modulation elements which areemployed at respective exposure heads. The GLVs are one kind ofMEMS-type (microelectro-mechanical systems) spatial light modulationelements (SLM: spatial light modulator), and are reflective diffractiongrating-type spatial light modulation elements. Other structures are thesame as in the exposure apparatus relating to the first embodiment.Accordingly, descriptions thereof will be omitted.

As shown in FIGS. 30, 31A and 31B, each of the exposure heads 166 ₁₁ to166 _(mn) is provided with a GLV 300 whose shape is long in apredetermined direction (a linear form), to serve as a spatial lightmodulation element for modulating the incident light beam at each of thepixels in accordance with the image data. At a light incidence side ofthe GLV 300, similarly to the first embodiment, the fiber array lightsource 66, the lens system 67 and the mirror 69 are disposed in thisorder.

The linear-form GLV 300 is disposed such that a long direction thereofis parallel with the direction of arrangement of the optical fibers ofthe fiber array light source 66, and reflection faces of ribbon-formmicrobridges of the GLV 300 are substantially parallel to the reflectionface of the mirror 69. The GLV 300 is connected to an unillustratedcontroller which controls the GLV 300.

At the GLV 300, as shown in FIG. 32, a large number (for example, 6,480)of microbridges 209, which are provided with ribbon-form reflectionsurfaces, are arranged in parallel on a long strip-form form support203, which is formed of silicon or the like. At the GLV 300, a largenumber of slits 211 are formed between adjacent microbridges 209.Ordinarily, one pixel is structured by a row of a plurality (forexample, six) of the microbridges 209. If it is assumed that each pixelis structured by a row of six microbridges, then exposure of 1,080pixels is possible with the 6,480 microbridges.

As shown in FIGS. 33A and 33B, at each microbridge 209, a reflectionelectrode film 209 b is formed on a surface of a flexible beam 209 a.The beam 209 a is formed of silicon nitride (SiNe) or the like, and thereflection electrode film 209 b is formed of a single-layer metallicfilm of aluminum (or gold, silver, copper or the like). Each of thereflection electrode films 209 b is connected to a power source byunillustrated wiring, via an unillustrated switch.

Now, a principle of operation of the GLV 300 will be briefly described.In a state in which voltage is not applied, the microbridge 209 has apredetermined spacing distance from the support 203. When a voltage isapplied between the microbridge 209 and the support 203, a staticelectricity attraction force is generated between the microbridge 209and the support 203 by induced static charge, and the microbridge 209flexes to the support 203 side thereof. Then, when the application ofvoltage is stopped, this flexure is released and the microbridge 209reverts elastically, thus separating from the support 203. Accordingly,by disposing microbridges to which voltage is applied and microbridgesto which voltage is not applied alternately, a diffraction grating canbe formed by the application of voltages.

FIG. 33A shows a case in which voltage is not applied to a row ofmicrobridges of a pixel unit, and the pixel unit is in an ‘OFF’ state.In the OFF state, the heights of reflection surfaces of the microbridge209 are all the same, optical path differences in reflected light arenot generated, and the reflected light is reflected normally. In otherwords, diffracted light only of the zero-th order can be obtained.Alternatively, FIG. 33B shows a case in which voltages are applied tothe microbridge row of the pixel unit, and the pixel unit is in an ‘ON’state. Note that the voltage is only applied to every second microbridge209. In the ON state, according to the principle described above,central portions of the microbridges 209 are flexed, and a reflectionsurface with alternating steps is formed. In other words, a diffractiongrating is formed. When laser light is made incident on this reflectionsurface, an optical path difference is generated between light that isreflected from the microbridges 209 that are flexed and light that isreflected from the microbridges 209 that are not flexed. Thus, lightwith a diffraction order of ±1 is emitted in a predetermined direction.

Accordingly, in accordance with control signals from the unillustratedcontroller, voltages are applied to drive the microbridge rows for therespective pixels of the GLV 300 for control between the ON and OFFstates. Thus, laser light that is incident at the GLV 300 is modulatedat each pixel and diffracted in the predetermined direction.

At the light reflection side of the GLV 300, that is, at the side towhich the diffracted light (zero-th order diffracted light and ±1storder diffracted light) is emitted, the lens systems 54 and 58, whichfocus the diffracted light onto the scanning surface (surface to beexposed) 56 are disposed such that the GLV 300 and the surface to beexposed 56 have a conjugative relationship. Furthermore, the ribbon-formreflection surfaces of the GLV 300 are disposed in advance to beinclined at a predetermined angle (for example, 45°) with respect to theoptical axis of the lens system 54, such that the diffracted light isincident at the lens system 54.

In FIGS. 31A and 31B, the zero-th order diffraction light is representedby broken lines and the ±1st order diffraction light is represented bysolid lines. The zero-th order diffraction light from the GLV 300 isfocused only in the longitudinal direction of the GLV by the lens system54. Accordingly, a shading plate 55 with a long strip form, which is foreliminating the zero-th order diffraction light from the optical path tothe scanning surface 56 is disposed between the lens system 54 and thelens system 58 such that the longitudinal direction of the shading plate55 intersects the longitudinal direction of the GLV 300.

The lens system 54 condenses the diffracted light that is incidentthereat in the longitudinal direction of the GLV 300, and makes thelight parallel in the sub-scanning direction. The long strip-formshading plate 55, which is for eliminating the zero-th order diffractedlight from the optical path to the scanning surface 56, is disposed at afocusing point of the zero-th order diffracted light between the lenssystem 54 and the lens system 58, such that the longitudinal directionof the shading plate 55 intersects the longitudinal direction of the GLVat right angle. As a result, the zero-th order diffracted light alone isselectively removed.

In this exposure head, image data corresponding to an exposure patternis inputted to the unillustrated controller connected to the GLV 300,and control signals are generated on the basis of this image data. Eachpixel unit of the microbridges of the GLV 300 at each exposure head isswitched on or off on the basis of the generated control signals. As aresult, the photosensitive material 150 is exposed in a unit with anumber of pixels substantially the same as the number of pixels at theGLVs 300. Thus, with sub-scanning due to movement of the stage 152, thestrip-form exposed regions are respectively formed by the exposureheads.

In the exposure apparatus of the present embodiment, because the GLV 300is a long strip-form spatial light modulation element whose width in ashort direction thereof is narrow, it is difficult to illuminate the GLV300 efficiently. However, as in the first embodiment, thehigh-brightness fiber array light source, at which the emission endportions of the optical fibers of the multiplex laser light source arearranged in an array pattern, is utilized at a light source forilluminating the GLV, and the cladding diameters of the emission ends ofthe optical fibers are smaller than the cladding diameters of theincidence ends thereof. Therefore, the sub-scanning direction diameterof the beam emitted from the laser emission portion 68 is small, and anangle of luminous flux that has passed through the lens system 67 andthe like and is incident on the GLV 300 is small. Thus, the GLV 300 canbe illuminated with high efficiency and a long depth of focus can beprovided. Moreover, because the multiplex laser light source isutilized, exposure with a high power output is possible and a lower costexposure apparatus can be provided.

Next, variant examples of the exposure apparatus described above will bedescribed.

Application of the Exposure Apparatus

The exposure apparatus described above may be suitably utilized forapplication to, for example, exposure of a dry film resist (DFR) in aprocess for fabricating a printed wiring board (PWB), formation of acolor filter in a process for fabricating a liquid crystal display(LCD), exposure of a DFR in a process for fabricating a TFT, exposure ofa DFR in a process for fabricating a plasma display panel (PDP), and thelike.

Further, the exposure apparatus described above may also be employed forvarious types of laser machining, such as laser ablation for vaporizing,dispersing or the like and hence removing a portion of a material bylaser irradiation, and for sintering, lithography and the like. Becausethe exposure apparatus described above has high power output and iscapable of exposing at high speed with a deep depth of focus, theexposure apparatus can be employed for fine-detail machining by laserablation or the like. For example, instead of carrying out developingprocessing to prepare a PWB, the exposure apparatus described above maybe employed for removing a resist in accordance with a pattern byablation, or for forming a pattern in a PWB by direct ablation withoutusing a resist. Further still, for a lab-on-a-chip, in which mixing,reaction, separation, detection and the like of numerous fluids areintegrated at a glass or plastic chip, the exposure apparatus describedabove can be employed for forming very small flow channels with groovewidths of tens of microns.

In particular, because the exposure apparatus described above utilizesthe GaN-based semiconductor lasers in the fiber array light sources, theexposure apparatus can be favorably employed for the above-mentionedlaser processes. Specifically, GaN-based semiconductor lasers can bedriven with short pulses, and sufficient power can be provided even forlaser ablation and the like. Further, because these are semiconductorlasers, unlike solid state lasers in which driving speeds are low, rapiddriving with a cycling frequency of around 10 MHz is possible, andhigh-speed exposure is possible. Further still, because metals have highoptical absorptivities for laser light with a wavelength in the vicinityof 400 nm, and readily convert such laser light to heat energy, laserablation or the like can be carried out rapidly.

In a case of exposing a liquid resist which is to be employed for TFTpatterning, a liquid resist which is to be employed for patterning acolor filter or the like, it is preferable that the material to beexposed is exposed in a nitrogen atmosphere, in order to prevent areduction in sensitivity (desensitization) due to oxygen inhibition.Consequent to such exposure in a nitrogen atmosphere, oxygen inhibitionof photopolymerization reactions is inhibited, sensitivity of the resistis raised, and rapid exposure is possible.

With the exposure apparatus described above, any of photon modephotosensitive materials, which are directly recorded with informationby exposure, and heat mode photosensitive materials, in which heat isgenerated by exposure and information is recorded thereby, may beemployed. In cases in which photon mode photosensitive materials areemployed, GaN-based semiconductor lasers, wavelength-conversion solidstate lasers and the like are employed as the laser apparatus, and incases in which heat mode photosensitive materials are employed,AlGaAs-based semiconductor lasers (infrared lasers) and solid statelasers are employed as the laser apparatus.

Other Spatial Modulation Elements For the first embodiment describedabove, examples of driving only a portion of the DMD micromirrors weredescribed. However, a long, thin DMD may be utilized in which a largenumber of micromirrors, whose reflection surface angles can berespectively altered in accordance with control signals, are arranged ina two-dimensional pattern on a support whose length in a directioncorresponding to a predetermined direction is longer than a lengththereof in a direction intersecting the predetermined direction. Whensuch a DMD is utilized, because the number of micromirrors whosereflection surface angles are to be controlled is smaller, modulationrates can be similarly increased.

For the first and second embodiments described above, exposure headswhich are provided with DMDs or GLVs as spatial modulation elements havebeen described. However, for example, MEMS (microelectro-mechanicalsystems) type spatial modulation elements (SLM: spatial lightmodulator), optical elements (PLZT elements), liquid crystal shutters(FLC) and the like, which modulate transmitted light by electro-opticaleffects, and spatial modulation elements other than MEMS types may beutilized. In these cases too, a pixel portion which is a subsection ofall of the pixels that are arranged on a support may be employed. Thus,modulation rates per pixel and per main scanning line can be madefaster, and the same effects as above can be provided.

Herein, MEMS is a general term for Microsystems in which micro-sizesensors, actuators and control circuits are integrated bymicro-machining technology based on IC fabrication processes. MEMS typespatial modulation elements means spatial modulation elements which aredriven by electro-mechanical operations by utilization of staticelectric forces.

Another Exposure Method

As shown in FIG. 18, the whole surface of the photosensitive material150 may be exposed by a single cycle of scanning in a direction X by thescanner 162, the same as in the embodiments described above.Alternatively, as shown in FIGS. 19A and 19B, scanning and displacementmay be repeated such that, after the photosensitive material 150 hasbeen scanned in the direction X by the scanner 162, the scanner 162 isdisplaced by one step in a direction Y and scanning is again carried outin the direction X. Thus, the whole surface of the photosensitivematerial 150 can be exposed by a plurality of scans. Note that in thisexample the scanner 162 is equipped with eighteen of the exposure heads166.

Other Laser Devices (Light Sources)

For the embodiments described above, examples in which the fiber arraylight sources that are utilized are equipped with pluralities ofmultiplex laser light sources have been described. However, the laserapparatus is not limited to a fiber array light source in whichmultiplexed laser light sources are arranged. For example, a fiber arraylight source may be utilized in which fiber light sources which are eachequipped with a single optical fiber, which emits laser light inputtedfrom a single semiconductor laser having one light emission point, arearrayed.

Further, for the embodiments described above, an example in which themultiplex laser light source that is utilized is provided with a laserarray in which, as shown in FIG. 20, the plurality (for example, seven)of chip-form semiconductor lasers LD1 to LD7 are arranged on a heatblock 100, has been described. However, the multiplex laser light sourceis not limited to a laser light source which multiplexes laser lightemitted from a plurality of chip-form semiconductor lasers.

As shown in FIG. 21A, a chip-form multi-cavity laser 110 in which aplurality (for example, five) of light emission points 110 a arearranged in a predetermined direction is known. For example, as shown inFIG. 22, a multiplex laser light source in which this multi-cavity laser110 is provided may be utilized. This multiplex laser light source isstructured with the multi-cavity laser 110, a single multi-mode opticalfiber 130 and a condensing lens 120. The multi-cavity laser 110 may bestructured with, for example, a GaN-based laser diode with anoscillation wavelength of 405 nm.

In comparison with cases in which chip-form semiconductor lasers arearranged, the multi-cavity laser 110 can be arranged with betterpositional accuracy of the light emission points. As a result, the laserbeams emitted from the respective light emission points are easier tomultiplex. However, if the number of light emission points is large,deformation of the multi-cavity laser 110 is likely to occur duringlaser fabrication. Therefore, it is preferable if the number of thelight emission points 110 a is not more than five.

In the structure described above, laser beams B, which are emittedrespectively from the plurality of light emission points 110 a of themulti-cavity laser 110, are condensed by the condensing lens 120 andinputted to a core 130 a of the multi-mode optical fiber 130. The laserlights that have been inputted to the core 130 a are propagated in theoptical fibers, multiplexed into a single beam, and emitted.

The plurality of light emission points 110 a of the multi-cavity laser110 may be lined up within a breadth that is substantially the same as acore diameter of the multi-mode optical fiber 130. As the condensinglens 120, a convex lens with a focal length substantially the same asthe core diameter of the multi-mode optical fiber 130, a rod lens whichcollimates the beams emitted from the multi-cavity laser 110 only in adimension which is orthogonal to active layers of the multi-cavity laser110, or the like may be utilized. By lining up the light emission points110 a and using such a lens, a coupling efficiency of the laser beams Binto the multi-mode optical fiber 130 can be raised.

Further, as shown in FIG. 21B, a multi-cavity laser array can beutilized in which a plurality of the multi-cavity lasers 110 arearranged on the heat block 100 in the same direction as the arrangementdirection of the light emission points 110 a of each of these chips. Asshown in FIG. 23, a structure of a multiplex laser array may be providedwith a laser array 140 in which a plurality (for example, nine) of themulti-cavity lasers 110 are arranged with a constant spacingtherebetween on a heat block 111. The plurality of multi-cavity lasers110 are arranged in the same direction as the direction of arrangementof the light emission points 110 a of each chip, and fixed.

The structure of this multiplex laser array includes the laser array140, a plurality of lens arrays 114, a single rod lens 113, the singlemulti-mode optical fiber 130 and the condensing lens 120. The pluralityof lens arrays 114 is disposed in correspondence with the multi-cavitylasers 110. The rod lens 113 is disposed between the laser array 140 andthe plurality of lens arrays 114. The lens arrays 114 are provided withpluralities of microlenses corresponding to the light emission points ofthe multi-cavity lasers 110.

In the structure described above, each of laser beams B that arerespectively emitted from the plurality of light emission points 110 aof the plurality of multi-cavity lasers 110 are condensed in apredetermined direction by the rod lens 113, and then made parallel bythe respective microlenses of the lens arrays 114. Laser beams L thathave been made parallel are condensed by the condensing lens 120 andinputted into the core 130 a of the multi-mode optical fiber 130. Thelaser light that has been fed in to the core 130 a is propagated in theoptical fiber, multiplexed to a single beam, and emitted.

Still another example of a multiplex laser light source will beillustrated. In this multiplex laser light source, as shown in FIGS. 24Aand 24B, a heat block 182, which is L-shaped in a section cut in thedirection of an optical axis, is mounted on a substantially rectangularheat block 180. An accommodation space is formed between the two heatblocks. At an upper face of the L-shaped heat block 182, a plurality(for example, two) of the multi-cavity lasers 110, in which pluralities(for example, five) of the light emission points are arranged in anarray pattern, are arranged with constant spacing in a direction thesame as the direction of arrangement of the light emission points 110 aof each chip, and fixed.

A recess is formed in the substantially rectangular heat block 180. Aplurality (for example, two) of the multi-cavity lasers 110, in whichpluralities (for example, five) of the light emission points arearranged in an array pattern, are disposed on a recess side of an upperface of the heat block 180, such that the light emission points thereofare disposed in the same vertical plane as the light emission points ofthe laser chips that are disposed at the upper face of the heat block182.

A collimation lens array 184, in which collimator lenses are arranged incorrespondence with the light emission points 110 a of each chip, isdisposed at a laser light emission side of the multi-cavity lasers 110.The collimation lens array 184 is disposed such that a longitudinaldirection of each collimator lens coincides with a direction in whichspreading angles of the laser beams are large (a fast axis direction)and the width direction of the each collimator lens coincides with adirection in which the spreading angles are small (a slow axisdirection). Accordingly, because the collimator lenses are arrayed andintegrated, a spatial utilization rate of the laser light can beimproved, and higher output can be provided by the multiplexed laserlight source. Moreover, the number of components can be reduced andcosts can be lowered.

The single multi-mode optical fiber 130 and the condensing lens 120 aredisposed at a laser light emission side of the collimation lens array184. The condensing lens 120 condenses and focuses the laser beams ontothe incidence end of the multi-mode optical fiber 130.

In the structure described above, respective laser beams, which areemitted from the pluralities of light emission points 110a of theplurality of multi-cavity lasers 110 disposed on the heat blocks 180 and182, are converted to parallel light by the collimation lens array 184,condensed by the condensing lens 120, and made to be incident on thecore 130 a of the multi-mode optical fiber 130. The laser light that isincident at the core 130 a is propagated in the optical fiber,multiplexed into a single beam, and emitted.

Because, in this multiplex laser light source, the multi-cavity lasersare disposed at a plurality of levels and the collimator lenses arearrayed as described above, a particularly high power output can beexpected. When this multiplexed laser light source is utilized, a fiberarray light source, a bundled fiber light source or the like with evenhigher luminance can be structured. Thus, this multiplex laser lightsource is particularly favorable for use as the fiber light sourcestructuring the laser light source of the exposure apparatus of thepresent invention.

The multiplex laser light source described above is accommodated in acasing, and a laser module in which an emission end portion of themulti-mode optical fiber 130 is led out from the casing can bestructured.

For the embodiments described above, examples have been described inwhich another optical fiber, which has the same core diameter as themulti-mode optical fiber but a smaller cladding diameter than themulti-mode mode optical fiber, is joined at the emission end of themulti-mode optical fiber of the multiplex laser array, and the fiberarray light source is thus designed to have a higher luminance. However,for example, as shown in FIGS. 35A and 35B, the multi-mode opticalfibers 30 may be employed with cladding diameters of 125 μm, 80 μm, 60μm or the like, and without joining other optical fibers at the emissionends thereof. When such optical fibers with small cladding diameters areemployed and two or three of the fiber light sources at which numerousbeams are multiplexed are arrayed as shown in FIG. 35B or bundled asshown in FIG. 35A, the light emission points can be brought closetogether, as a point-like light source. Consequently, structure of theoptical system that is used in this light source is simple. Accordingly,this light source can be structured with a low cost, high functionalityoptical system.

FIG. 36 shows end faces (a light emission portion) of the laser emissionportion 68 of FIG. 35A. The multi-mode optical fibers 30 are bundledsuch that adjacent the optical fibers are as close to each other aspossible. Because, as described above, cladding diameters of themulti-mode optical fibers 30 are all 125 μm, the size of the lightemission portion is about 0.375 mm by 0.25 mm. Further, as describedabove, the output of the laser emission portion 68 is about 1 W. Thus,in comparison with a conventional bundled fiber light source, the samelaser output can, be provided with about one-seventh the number offibers, about one-third the light emission portion diameter, and aboutone-tenth the light emission region area.

Accordingly, because the number of multi-mode optical fibers (the numberof laser modules) can be reduced, a lowering in costs of the lightsource can be expected. Further, by reducing the number of opticalfibers, the light emission portion diameter can be made smaller. Thus, aluminance about ten times higher can be expected.

As mentioned above, an example in which a plurality of optical fiberswith different cladding diameters are joined into an optical fiber inwhich the cladding diameter of the emission end is smaller than thecladding diameter of the incidence end has been described. However, itis also possible to structure the optical fibers such that the claddingdiameter gets smaller from the incidence end to the emission endgradually.

Light Amount Distribution-Correcting Optical System

In the embodiments described above, a light intensitydistribution-correcting optical system formed of a single pair ofcombination lenses is used at the exposure head. The light intensitydistribution-correcting optical system converts an optical flux width ateach of emission positions such that a ratio of a flux width at aperipheral edge portion to a flux width at a central portion, which isnear an optical axis, is smaller at an emission side of the lightintensity distribution-correcting optical system than at an incidenceside thereof, and corrects the light intensity distribution such that alight intensity distribution at irradiated surfaces of the DMD or thelike is substantially uniform when the parallel flux from the lightsource is irradiated at the DMD. Operation of this light intensitydistribution-correcting optical system will be described.

First, as shown in FIG. 25A, a case in which the overall luminous fluxwidths (total flux widths) H0 and H1 of incidence luminous flux andemission luminous flux are the same is described. In FIG. 25A, theportions indicated by the reference numerals 51 and 52 represent,virtually, an incidence plane and an emission plane of the lightintensity distribution-correcting optical system.

In the light intensity distribution-correcting optical system, luminousflux widths h0 of luminous flux that is incident at a central portionnear to an optical axis Z1, and luminous flux width h1 of luminous fluxthat is incident at a peripheral edge portion are set to be the same(h0=h1). The light intensity distribution-correcting optical systemimplements operations on the luminous flux widths h0 and h1 at theincidence side, which are equal, so as to expand the luminous flux widthh0 for the incident flux of the central portion and, conversely, tocontract the luminous flux width h1 for the incident light of theperipheral edge portion. That is, for a width h10 of emission luminousflux of the central portion and a width h11 of emission luminous flux ofthe peripheral edge portion, h11 is made to be less than h10.Represented as a ratio of flux widths, at the emission side, a ratio ofthe luminous flux width at the peripheral edge portion to the luminousflux width at the central portion, (h11/h10) is smaller than the ratio(h1/h0=1) at the incidence side (i.e., h11/h10<1).

When the luminous flux widths are converted in this manner, the flux atcentral portions, at which the luminous flux distribution is usuallylarge, can be shifted to peripheral edge portions, at which lightintensities are usually insufficient. Thus, the light intensitydistribution can be made uniform at the irradiated surfaces without adrop in efficiency of utilization of the light as a whole. The degree towhich the luminous flux is made uniform is such that, for example,unevenness of light intensities inside an effective region is within30%, and preferably within 20%.

Operation and effects of this light intensity distribution-correctingoptical system are the same in a case in which the overall flux widthchanges between the incidence side and the emission side (see FIGS. 25Band 25C).

FIG. 25B shows a case in which the overall flux width HO at theincidence side is “contracted” to a width H2 and emitted (H0>H2). Inthis case too, the light intensity distribution-correcting opticalsystem acts on the light which has flux widths at the incident side h0and h1, which are equal, to make the flux width h10 of the centralportion at the emission side greater in comparison to the peripheraledge portion and, in contrast, to make the flux width h11 of theperipheral edge portion smaller in comparison to the central portion. Interms of a contraction ratio of the flux, the light intensitydistribution-correcting optical system implements operation such that acontraction ratio relative to the incident luminous flux is smaller atthe central portion than at the peripheral edge portion and acontraction ratio relative to the incident luminous flux is larger atthe peripheral edge portion than at the central portion. In this casetoo, the ratio of the flux width at the peripheral edge portion to theflux width at the central portion (h11/h10) is smaller than the ratio(h1/h0=1) at the incidence side (i.e., h11/h10<1).

FIG. 25C shows a case in which the overall flux width H0 at theincidence side is “expanded” to a width H3 and emitted (H0<H3). In thiscase too, the light intensity distribution-correcting optical systemacts on the light which has flux widths at the incident side h0 and h1,which are equal, to make the flux width h10 of the central portion atthe emission side greater in comparison to the peripheral edge portionand, in contrast, to make the flux width h11 of the peripheral edgeportion smaller in comparison to the central portion. In terms of anexpansion ratio of the flux, the light intensity distribution-correctingoptical system implements operation such that an expansion ratiorelative to the incident luminous flux is greater at the central portionthan at the peripheral edge portion, and an expansion ratio relative tothe incident luminous flux is smaller at the peripheral edge portionthan at the central portion. In this case too, the ratio of the fluxwidth at the peripheral edge portion relative to the flux width at thecentral portion (h11/h10) is smaller than the ratio (h1/h0=1) at theincidence side (i.e., h11/h10<1).

Thus, the light intensity distribution-correcting optical system changesthe luminous flux widths at each emission position, and makes ratios ofluminous flux widths at peripheral edge portions to luminous flux widthsat central portions, which are close to the optical axis Z1, smaller atthe emission side than at the incidence side. Thus, at the emissionside, light that has flux widths that are equal at the incidence sidehas flux widths at central portions that are greater than at peripheraledge portions, and flux widths at the peripheral edge portions becomesmaller than at the central portions. Hence, the flux of the centralportions can be shifted towards the peripheral edge portions, and aluminous flux cross-section whose light intensity distribution has beenmade uniform can be formed without bringing down light usage efficiencyof the optical system as a whole.

Next, one example of specific lens data of the combination lenses thatare employed as the light intensity distribution-correcting opticalsystem will be illustrated. In this example, lens data is illustratedfor a case in which, as in cases in which the light source is a laserarray light source, the light intensity distribution of a cross-sectionof emitted flux is a gaussian distribution. Now, in a case in which asingle semiconductor laser is connected to the incidence end of asingle-mode optical fiber, the light intensity distribution of emittedflux from the optical fiber will be a gaussian distribution. This isalso applicable in cases such as the present embodiments. Furthermore,this is also applicable to a case in which light intensities at centralportions, which are close to the optical axis, are greater than lightintensities at peripheral edge portions because the core diameter of amulti-mode optical fiber has been made smaller, approaching thestructure of a single-mode optical fiber, or the like.

Basic lens data is shown in the following table 1. TABLE 1 Basic LensData Si ri di Ni (surface (radius of (surface separation) (refractivenumber) curvature) (mm) index) 01 aspherical 5.000 1.52811 surface 02 850.000 03 8 7.000 1.52811 04 aspherical surface

As can be seen from table 1, the single pair of combination lenses isstructured by two aspherical-faced lenses with rotational symmetry. If aface at the light incidence side of a first lens, which is disposed atthe light incidence side of the pair, is considered to be a first face,and a face at the emission side of the first lens considered to be asecond face, the first face has an aspherical surface form. If a face atthe light incidence side of a second lens, which is disposed at thelight emission side of the pair, is considered to be a third face and aface at the light emission side of the second lens is considered to be afourth face, the fourth face has an aspherical surface form.

In table 1, surface number Si represents the number of the i-th surface(i=1 to 4), radius of curvature ri represents the radius of curvature ofthe i-th surface, and surface distance di represents a surface spacing,on the optical axis, between the i-th surface and the (i+1)-th surface.The dimension of surface distance di is millimeter (mm). Refractiveindex Ni represents the value of an index of refraction, for wavelength405 nm, of the optical element at which the i-th surface is provided.

A spherical surface data of the first and fourth surfaces is shown inthe following table 2. TABLE 2 Aspherical Surface Data First SurfaceFourth Surface C −1.4098E−02  −9.8506E−03  K −4.2192E+00  −3.6253E+01 a3 −1.0027E−04  −8.9980E−05  a4 3.0591E−05 2.3060E−05 a5 −4.5115E−07 −2.2860E−06  a6 −8.2819E−09  8.7661E−08 a7 4.1020E−12 4.4028E−10 a81.2231E−13 1.3624E−12 a9 5.3753E−16 3.3965E−15 a10 1.6315E−18 7.4823E−18

The aspherical surface data shown above represents factors in thefollowing formula (A), which represents aspherical surface forms.$\begin{matrix}{Z = {\frac{C \cdot \rho^{2}}{1 + \sqrt{1 - {K \cdot \left( {C \cdot \rho} \right)^{2}}}} + {\sum\limits_{i = 3}^{10}{a\quad{i \cdot \rho^{i}}}}}} & (A)\end{matrix}$

Each of the factors in the above formula (A) is defined as follows.

-   -   Z: length (mm) of a vertical line descending, in a plane        tangential to an apex point of the aspherical surface (a flat        plane pependicular to the optical axis), from a point on the        aspherical surface which is positioned at a height ρ from the        optical axis    -   ρ: distance from the optical axis (mm)    -   K: a coefficient of conicality    -   C: a rate of curvature near the axis (1/r, r being a near-axis        radius of curvature)    -   ai: an i-th aspherical surface coefficient (i=3 to 10)

In the numerical values shown in table 2, the symbol “E” signifies thatthe number following the E represents a decimal exponent, and that thenumber preceding the E is to be multiplied by a value represented by thedecimal exponent. For example, “1.0E-2” represents 1.0×10⁻².

FIG. 27 shows a light intensity distribution of illumination lightprovided by the single pair of combination lenses illustrated in table 1and table 2 above. The horizontal axis shows co-ordinates from theoptical axis, and the vertical axis shows light intensity ratios (%).For comparison, FIG. 26 shows a light intensity distribution ofillumination light in a case in which the correction is not carried out(a gaussian distribution). As can be seen from FIGS. 26 and 27, becausethe correction is carried out by the light intensitydistribution-correcting optical system, a light intensity distributionwhich is substantially uniform in comparison to the case in which thecorrection is not carried out can be obtained. Thus, exposure withuniform laser light that is free of unevenness can be carried outwithout reducing the efficiency of utilization of the light in theexposure head.

An example of a light intensity distribution correcting optical systemhas been shown. However, conventionally known means, such as a rodintegrator, a fly-eye lens array or the like may be used.

Another Imaging Optical System

In the first embodiment described above, two groups of lenses aredisposed to serve as an imaging optical system at the light reflectionside of the DMD employed in the exposure head. However, a couplingoptical system which widens and focuses the laser light may be disposedthereat. By widening the cross-sectional area of optical flux linesreflected by the DMD, an exposure area at the surface to be exposed (animaging region) can be enlarged to a desired size.

For example, as shown in FIG. 28A, the exposure head may be structuredwith the DMD 50, an illumination apparatus 144, lens systems 454 and458, a microlens array 472, an aperture array 476, and lens systems 480and 482. The illumination apparatus 144 illuminates laser light onto theDMD 50. The lens systems 454 and 458 widen and focus laser light thathas been reflected at the DMD 50. A large number of microlenses 474 aredisposed at the microlens array 472, in respective correspondence withthe pixels of the DMD 50. The aperture array 476 is provided with alarge number of apertures 478 in respective correspondence with themicrolenses of the microlens array 472. The lens systems 480 and 482focus laser light that has been transmitted through the apertures ontothe surface to be exposed 56.

In this exposure head, when laser light is irradiated from theillumination apparatus 144, the cross-sectional area of luminous fluxlines reflected in the ‘ON’ direction by the DMD 50 is enlarged to amagnification (for example, ×2) by the lens systems 454 and 458. Theenlarged laser light is condensed in accordance with the pixels of theDMD 50 by the microlenses of the microlens array 472, and is passedthrough the corresponding apertures of the aperture array 476. The laserlight that has passed through the apertures is imaged on the surface tobe exposed 56 by the lens systems 480 and 482.

In this imaging optical system, because the laser light that has beenreflected by the DMD 50 is enlarged to a certain magnification by theenlarging lens systems 454 and 458 and then projected on the surface tobe exposed 56, the overall image region becomes larger. Here, if themicrolens array 472 and the aperture array 476 is not disposed in thesystem, then, as shown in FIG. 28B, a one-pixel size (spot size) of eachbeam spot BS that is projected onto the surface to be exposed 56 willhave a size corresponding to the size of an exposure area 468, and anMTF (modulation transfer function) characteristic representing sharpnessof the exposure area 468 will fall.

In contrast, in the case in which the microlens array 472 and aperturearray 476 are disposed in the system, the laser light that has beenreflected by the DMD 50 is condensed in correspondence with the pixelsof the DMD 50 by the microlenses of the microlens array 472. As aresult, as shown in FIG. 28C, even though the exposure area is enlarged,the spot size of each beam spot BS can be shrunk to a desired size (forexample, 10 μm by 10 μm). Thus, the reduction of the MTF characteristiccan be prevented, and high precision exposure can be carried out. Notethat the exposure area 468 is inclined because the DMD 50 is disposed atan angle so as to eliminate gaps between pixels.

Moreover, even if the beams are broadened by aberration of themicrolenses, the beams can be smoothed by the apertures such that thespot sizes on the surface to be exposed 56 have a certain size. Inaddition, by this transmission through the apertures provided incorrespondence with the pixels, crosstalk between adjacent pixels can beprevented.

By employing the illumination apparatus 144 as a high-brightness lightsource in the same way as in the embodiments described above, the angleof flux that is incident on the microlenses of the microlens array 472from the lens system 458 is made small. Thus, incidence of portions ofthe flux at neighboring pixels can be prevented. Thus, a high extinctionratio can be realized. The extinction ratio could also be furtherimproved by making the aperture diameters smaller to cut excess light,but light intensity losses would be large. In contrast, in the presentexample the extinction ratio can be improved without increasing lightintensity losses.

Another Structure of Connected Optical Fibers

With FIG. 10, an example has been described in which the incidence endface of the optical fiber 31 is fused and joined at the emission endface of the multi-mode optical fiber 30. However, as shown in FIG. 40,it is also possible to form a small diameter portion 30 c at a distalend portion of the laser light emission side of the multi-mode opticalfiber 30 whose cladding diameter is large, and to coaxially join theoptical fiber 31, with a small cladding diameter and a length of 100 mmto the small diameter portion 30 c. A connection method for this opticalfiber is described next.

As the multi-mode optical fiber 30 and the optical fiber 31, any of stepindex-type optical fibers, graded index-type optical fibers andmultiplex-type optical fibers can be used. For example, step index-typeoptical fibers produced by Mitsubishi Cable Industries, Ltd. can beutilized. In the present embodiment, the multi-mode optical fiber 30 andthe multi-mode optical fiber 31 are step index-type optical fibers. Forthe multi-mode optical fiber 30, cladding diameter=125 μm, corediameter=50 μm, NA=0.2, and transmittance of the end face coating=99.5%or more. For the optical fiber 31, cladding diameter=60 μm, corediameter=50 μm, and NA=0.2.

Optical Fiber Connection Methods

Conventionally, since the tapered region of the cladding could not beobtained for a sufficient length, the tapered region included only thedistal end of the cladding. Accordingly, it was difficult to closelydispose the claddings to arrange the claddings in a array or a bundle,and to obtain a high-brightness light source. Furthermore, since it wasdifficult to arrange the cladding diameters evenly, it was difficult toform a uniform fiber array.

Accordingly, connecting separate optical fibers, whose claddingdiameters are smaller, to distal ends of optical fibers that are usuallyemployed for light propagation, and bundling portions of these opticalfibers whose cladding diameters are smaller has been considered.Conventionally, to connect two optical fibers in such a manner, electricdischarge-type fusion-splicing devices, which fuse and splice endportions of two optical fibers which have been coaxially aligned, arewidely used.

However, in a case in which two optical fibers having a large differencein external diameters (cladding diameters) thereof are fusion-spliced inthis manner, if electric discharge conditions are specified such thatthe thicker of the optical fibers is suitably melted, the thinner of theoptical fibers is excessively melted and the distal end thereof becomesrounded. Hence, the two optical fibers cannot be suitablyfusion-spliced. Conversely, if the electric discharge conditions arespecified such that the thinner of the optical fibers is suitablymelted, the electrical discharge is weak, and the thicker of the opticalfibers is not melted. Consequently, in this case too, the two opticalfibers cannot be tightly contacted and suitably fusion-spliced.Specifically, in cases depending on this conventional method, losses ofthe order of 1 dB may occur at the connection portion, and a connectionefficiency may be limited to around 80%.

According to a connection method described below, two optical fibershaving a large difference in external diameter can be reliablyconnected. This optical fiber connection method will be described withreference to FIGS. 37A and 37B. A present example, as shown in FIGS. 37Aand 37B, is an example in which the distal end portion of the multi-modeoptical fiber 30, whose external diameter (cladding diameter) is 125 μm,is connected with the multi-mode optical fiber 31 whose externaldiameter (cladding diameter), being 60 μm, is smaller. As an example,the multi-mode optical fiber 30 is a step index-type optical fiber, inwhich the core 30 a is covered with a cladding 30 b, whose refractionindex is lower than that of the core 30 a. Similarly, at the multi-modeoptical fiber 31, the core 31 a is covered with a cladding 31 b, whoserefraction index is lower than that of the core 31 a.

At the multi-mode optical fiber 30, cladding diameter=125 μm, corediameter=50 μm, NA=0.2, and transmittance of the end face coating=99.5%or more. At the multi-mode optical fiber 31, cladding diameter=60 μm,core diameter=50 μm, and NA=0.2.

First, as shown in FIG. 37A, mechanical machining such as grinding orthe like is applied to the cladding 30 b at the distal end portion ofthe core 30 a. Thus, the small diameter portion 30 c is formed with alength of the order of around 100 mm. The external diameter of thissmall diameter portion 30 c is 60 μm, the same as the cladding diameterof the multi-mode optical fiber 31.

Next, as shown in FIG. 37B, at the distal end of the small diameterportion 30 c described above, the multi-mode optical fiber 31, whoseexternal diameter is the same as portion 30 c, is fusion-spliced in astate in which the core axes of the small diameter portion 30 c and themulti-mode optical fiber 31 are coaxially aligned with one another. Forthis fusion, an ordinary electric discharge-type fusion-splicing devicewhich is used for fusing such optical fibers may be used. Examples ofsuch optical fiber fusion-splicing devices include a compact direct coremonitoring optical fiber fusion splicer SUMIOFCAS TYPE-37, from SumitomoElectric Industries, Ltd., and the like.

In the method described above, the small diameter portion 30 c is formedat the distal end portion of the multi-mode optical fiber 30, and thenthe optical fiber 31 having the same external diameter as the smalldiameter portion 30 c is fusion-spliced thereto. Therefore, the twooptical fibers 30 and 31 can be connected simply and reliably without,as in cases of fusing and connecting two optical fibers whose externaldiameters differ greatly, the external diameter of the optical fiber 31whose external diameter is smaller being excessively melted or,conversely, the external diameter of the optical fiber 30 whose externaldiameter is larger not being melted. Specifically, losses at theconnection portion of the two optical fibers 30 and 31 can be suppressedto around 0.05 dB, and a connection efficiency of 99% can be realized.

As described later, a plurality of optical fibers in which the twooptical fibers 30 and 31 are connected are prepared, and the distal endportions of the optical fibers 31 thereof are bundled for employment.Here, because the small diameter portions 30 c of the distal endportions of the multi-mode optical fibers 30 are not bundled, amechanical machining precision that is required at the small diameterportions 30 c is not particularly high, and the small diameter portions30 c can accordingly be formed with ease.

Next, another optical fiber connection method will be described, withreference to FIG. 38. In FIG. 38, the same reference numerals areapplied to elements that are the same as elements in FIG. 37, anddescriptions thereof that are not particularly necessary will be omitted(and the same applies hereafter).

In this example, a small diameter portion 30 c′ with a length of, forexample, around 100 mm, is formed by applying mechanical machining, suchas grinding or the like, to the cladding 30 b at the distal end portionof the multi-mode optical fiber 30. The external diameter of this smalldiameter portion 30 c′ is set to 80 μm, which is a little greater thanthe 60 μm cladding diameter of the multi-mode optical fiber 31. Next,the distal end of the small diameter portion 30 c′ is fusion-splicedwith the multi-mode optical fiber 31, whose external diameter is alittle smaller than that of the small diameter portion 30 c′, in a statein which the core diameters of the small diameter portion 30 c′ and themulti-mode optical fiber 31 are coaxially aligned with one another.

In the above-described case too, the two optical fibers 30 and 31 can beconnected simply and reliably without, as in a case of fusing andconnecting the multi-mode optical fiber 31 directly to the distal endportion of the multi-mode optical fiber 30 in which case the externaldiameters of the two optical fibers differ greatly, the optical fiber 31whose external diameter is smaller being excessively melted or,conversely, the optical fiber 30 whose external diameter is larger notbeing melted.

Next, yet another optical fiber connection method will be described,with reference to FIG. 39. In this example, first, the distal endportion of the multi-mode optical fiber 30 is fusion-spliced with amulti-mode optical fiber 32 having an external diameter of 80 μm, whichis smaller than the external diameter of the multi-mode optical fiber 30and larger than the external diameter of the multi-mode optical fiber31. Then the distal end portion of the multi-mode optical fiber 32 withthe intermediate diameter is fusion-spliced with the multi-mode opticalfiber 31 whose external diameter is smaller than that of the multi-modeoptical fiber 32.

As described above, when the multi-mode optical fiber 32 whose externaldiameter does not differ greatly from that of the multi-mode opticalfiber 30 is fusion-spliced to the multi-mode optical fiber 30, theexternal diameter of the optical fiber 32 whose external diameter issmaller is not excessively melted and, conversely, the optical fiber 30whose external diameter is larger does not fail to be melted. Further,when the multi-mode optical fiber 31 whose external diameter does notdiffer greatly from that of the multi-mode optical fiber 32 isfusion-spliced to the multi-mode optical fiber 32, the external diameterof the optical fiber 31 whose external diameter is smaller is notexcessively melted and, conversely, the optical fiber 32 whose externaldiameter is larger does not fail to be melted. As a result, the twooptical fibers 30 and 31 can be easily and reliably connected.

Conversely to the above, the multi-mode optical fiber 30 and multi-modeoptical fiber 32 may be fusion-spliced after the optical fiber 31 andmulti-mode optical fiber 32 have been fusion-spliced. In this case too,the same effects as described above are obtained.

APPLICATION EXAMPLES

The exposure apparatus of the present invention may be suitably appliedto an optical modelling device in which a light beam exposes aphoto-curable resin to form a three-dimensional model, a laminationmodelling device which sinters a powder with a light beam to formsintered layers and accumulates the sintered layers to form athree-dimensional model which is formed by a sintered powder body, andthe like.

For example, FIG. 34 shows structure of an optical modelling device inwhich the present invention is applied. This optical modelling device isprovided with a tank 556 whose top opens. A photocurable resin 550 isaccommodated in the tank 556. A flat board-like ascending/descendingstage 552 is disposed in the tank 556. This ascending/descending stage552 is supported by a support portion 554 which is disposed outside thetank 556. A female screw portion 554A is provided at the support portion554. This female screw portion 554A is screwingly engaged with a leadscrew 555 which is driven to rotate by an unillustrated driving motor.The ascending/descending stage 552 ascends and descends in accordancewith the rotation of the lead screw 555.

Above a liquid surface of the ascending/descending stage 552accommodated in the tank 556, a box-like scanner 562 is disposed withlong sides thereof oriented in a direction of short sides of the tank556. The scanner 562 is supported by two support arms 560, which areattached at two side faces in a short side direction of the scanner 562.The scanner 562 has the same structure as the scanners in theembodiments described above, is provided with a plurality of exposureheads, and is connected to an unillustrated controller which controlsthe exposure heads.

Respective guides 558, which extend in a longitudinal direction, areprovided at two side faces in a long side direction of the tank 556.Lower end portions of the two support arms 560 are attached at theseguides 558 so as to be reciprocally movable along the longitudinaldirection. In this optical modelling device, an unillustrated drivingapparatus is provided for moving the support arms 560 and the scanner562 along the guides 558.

In this optical modelling device, the scanner 562 is moved at a constantspeed along the guides 558, from an upstream side to a downstream sidein the longitudinal direction, by the unillustrated driving apparatus.In accordance with the movement of the scanner 562 at the constantspeed, the liquid surface of the photocurable resin 550 is scanned, anda strip-form cured region is formed by each recording head. When curingof a portion corresponding to one layer by one cycle of sub-scanning bythe scanner 562 has been completed, the scanner 562 is returned alongthe guides 558 by the unillustrated driving device to a start point atan upstream-most side. Then the lead screw 555 is rotated by theunillustrated driving motor, and the ascending/descending stage 552descends by a predetermined amount. Thus, the cured portion of thephotocurable resin 550 is submerged below the liquid surface, and theliquid-form photocurable resin 550 fills the space above the curedportion. Hence, the sub-scanning is carried out by the scanner 562repeatedly. In this manner, exposure (curing) by the sub-scanning andlowering of the stage is carried out repeatedly and, by accumulating thecured portions, a three-dimensional model is formed. Because thehigh-brightness laser apparatus of the present invention is utilized atthe exposure heads of the scanner 562, deep focal depth can be obtained.Thus, modelling can be carried out with high-speed and high accuracy.

According to the present invention, a high-brightness laser apparatus isprovided. Further, when an exposure apparatus and/or exposure head ofthe present invention utilizes this high-brightness laser apparatus, aneffect that deep depth of focus can be obtained is additionallyproduced. Further still, in the case of an area-type exposure beam, aneffect that beam blurring at peripheral edge portions can be suppressedis provided. Further yet, in a case in which a multiplex laser lightsource is utilized as the high-brightness laser apparatus, an effectthat the exposure apparatus and exposure head can be designed for higheroutput and lower costs is obtained.

1. An exposure using an exposure head, the exposure head including alaser apparatus having a fiber light source which includes an opticalfiber with an incidence end and an emission end, a spatial modulationelement including numerous pixel portions which are arranged in atwo-dimensional form on a support and an optical system, the methodcomprising: emitting laser light by the fiber light source that entersthe incidence end of the optical fiber from the emission end of theoptical fiber, the optical fiber including an optical fiber having auniform core diameter and a cladding diameter of the emission end whichis smaller than a cladding diameter of the incidence end; modulatinglaser light irradiated from the laser apparatus by the spatialmodulation element, the light modulation states being changed inaccordance with respective control signals; and focusing laser lightthat has been modulated at the pixel portions by the optical system onan exposure surface.
 2. The exposure method of claim 1, wherein thespatial modulation element comprises a micromirror device which includesnumerous micromirrors arranged in the two-dimensional form on thesupport, angles of reflection surfaces of the micromirrors beingchangeable in accordance with the respective control signals.
 3. Theexposure method of claim 1, wherein the spatial modulation elementcomprises a grating light valve which includes numerous movable grilles,which are provided with ribbon-like reflection surfaces and are movablein accordance with the control signals, and fixed grilles, which areprovided with ribbon-like reflection surfaces, the numerous movablegrilles and fixed grilles being alternately disposed in parallel.
 4. Theexposure method of claim 1, further comprising: condensing the laserlight at each pixel by a microlens array provided at an emission side ofthe spatial modulation element which includes microlenses which aredisposed in correspondence with the pixel portions of the spatialmodulation element.
 5. The exposure method of claim 1, furthercomprising: making luminous flux from the laser apparatus parallel fluxby a collimator lens; converting a luminous flux width by a light amountdistribution-correcting optical system at each of emission positionsthereof such that a ratio of a luminous flux width at a peripheral edgeportion to a luminous flux width at a central portion, which is near anoptical axis, is smaller at an emission side of the light amountdistribution-correcting optical system than at an incidence sidethereof; and correcting a light amount distribution of the laser lightthat has been converted to parallel flux by the collimator lens so as tobe substantially uniform at irradiated surfaces of the spatialmodulation element, wherein the collimator lens and the light amountdistribution-correcting optical system are disposed between the laserapparatus and the spatial modulation element.
 6. The exposure method ofclaim 1, further comprising: moving the exposure head by a moving meansrelatively with respect to the exposure surface.